TESTING THE EFFECTIVENESS OF TWO METHODS FOR SELECTIVELY TRAPPING LIONFISH AND ESTIMATING THE FEASIBILITY OF A COMMERCIAL LIONFISH FISHERY ON SABA
BACHELOR THESIS
TOM BROKKE & MARC VELDMAN VAN HALL LARENSTEIN
SABA BANK MANAGEMENT UNIT 2019
TESTING THE EFFECTIVENESS OF TWO METHODS FOR SELECTIVELY TRAPPING LIONFISH AND ESTIMATING THE FEASIBILITY OF A
COMMERCIAL LIONFISH FISHERY ON SABA
Bachelor Thesis
Authors:
Tom Brokke (Student Van Hall Larenstein) 000002265
&
Marc Veldman (Student Van Hall Larenstein) 000002626
Supervisors:
Joop van Eerbeek (Van Hall Larenstein)
Lecturer and Researcher Marine Biology and Ecology Coastal and Marine Management
&
Marlous Heemstra (Van Hall Larenstein)
Lecturer and Program Manager Coastal and Marine Management Commissioned by:
Ayumi Kuramae Izioka (Saba Bank Management Unit) Saba Bank Sr. Program Coordinator
Module:
LKZ428VNA01 - Final Thesis
Cover photo: (Novak, 2015)
Leeuwarden, The Netherlands October 17, 2019
Abstract
The invasive lionfish (Pterois volitans and Pterois miles) started invading the Caribbean Sea since the 1980’s and were first sighted on the Saba Bank since 2009 where they established themselves fully during the following two years. They have no specific preference for prey species and their predation on juveniles also heavily diminishes commercially and ecologically important fish stocks. Lionfish are particularly hard to control because they have virtually no natural predators in this region, they can produce up to 15.000 eggs every four days throughout the whole year, and they can tolerate a wide variety of habitat conditions. A multitude of regional culling programs have been developed in the Caribbean, many focused in the shallower near-shore areas. In order to offer a possible alternative for deep-water snapper fisheries on the Saba Bank for fishermen during a possible future closed season, experiments with trapping lionfish selectively using two altered fish traps designs have been conducted on the far eastern side of the Saba Bank over the period of May 2018 till September 2019, this to identify the most effective method of trapping lionfish. The two lionfish traps both utilized an artificial fish aggregation device represented by a plastic crate with open sides. One design has three escape funnels attached to its side to allow for bycatch escape. In total 275 traps have been hauled over a depth range between 60-450 feet. A market study has been conducted as well, which aimed to map the economic feasibility of a commercial lionfish fishery. Restaurants, fishermen and the general public have been approached with questionnaires to identify the current state of awareness, supply and demand and prices of lionfish on Saba. Based upon the information from both the trap study and market study, calculations could be made to estimate the economic value of lionfish using the most effective method. No significant differences could be found between the number of lionfish in both trap designs. Usage of the funnel trap design significantly reduced the amount of bycatch and the number of bycatch species compared to the traditional trap. The funnel design had an average of 4,71 bycatch individuals and 2,52 species and the traditional had 12,38 bycatch individuals and 3,98 species on average. A significant decrease in both bycatch individuals and bycatch species was detected with increasing fishing depth. Blackfin snapper (Lutjanus buccanella) was the most abundant bycatch in both trap designs followed by yellow-eye snapper (Lutjanus vivanus), vermillion snapper (Rhomboplites aurorubens) and red hind (Epinephelus guttatus). These four species comprised of 78,09% of all bycatch and are coincidentally the target species for redfish fisheries on the Saba Bank.
When an effectiveness score was given to each individual trap it showed that the funnel trap scored significantly higher than a traditional trap. The market study showed that a commercial market for lionfish could be possible on Saba however, demand is higher than supply can deliver. Restaurants are the chief customer and the price for which restaurant buys lionfish was $3,50 per pound. It was concluded that if fishermen would be adopting the funnel lionfish trap design right now and start fishing for lionfish instead of redfish, they would not catch enough lionfish for it to be economically feasible, and bycatch would still mostly be redfish. For a commercial lionfish fishery to be feasible fishermen might need to up their willingness to accept for a pound of lionfish to the redfish standard of $5 per pound, and restaurants need to be willing to pay this. More research is needed, and it is advised to continue the lionfish trapping experiment with minor adjustments into its methods, regarding the possible use of a lionfish dummy and utilizing different areas of the Saba Bank.
Acknowledgements
We would like to thank the Saba Conservation Foundation and the Saba Bank Management Unit for commissioning this project, and for providing us with workspace and the required materials to execute this project and also, we would like express our gratitude towards our supervisor Ayumi Kuramae Izioka from the Saba Bank Management Unit for her help during construction of traps, the data collection, and her advice and feedback throughout the course of this project. We would like to thank our supervisors, Marlous Heemstra and Joop van Eerbeek from Van Hall Larenstein
Leeuwarden for their valuable time, feedback and advise during the writing of the thesis proposal and this thesis report.
This thesis would not have been possible without the support and funding of the
World Wildlife Fund for Nature-Caribbean (WWF-Caribbean), and the Dutch Ministry of Economic Affairs.
Without the financial support for housing from Wageningen Marine Research we would not have been able to live on Saba and for that we would like to show our appreciation.
Our gratitude also extends to Bradley Johnson, who was helpful enough to take us out to the Saba Bank on multiple occasions with his own fishing vessel the Second Wind to deploy and haul our traps, while teaching us some valuable fishing lessons.
We would like to thank the Island Government for being kind enough to donate a bunch of blue plastic crates to be used as fish aggregations devices.
And last, but not least, we would like to give a special thanks to the volunteers who have helped us underneath the beating sun with construction of the lionfish traps, who ventured with us to the Bank to help us haul the traps and measure their contents and who’s company we appreciated.
Table of contents
1 Introduction ... 5
2 Background information ... 9
2.1 Description of lionfish biology ... 9
2.2 Description of Saba bank fisheries ... 9
2.3 Lionfish eradication programs in the Caribbean ... 10
2.4 Change in attitude towards lionfish consumption ... 12
3 Materials and methods ... 13
3.1 Research area ... 13
3.2 Methods of trap study ... 14
3.2.1 Data collection ... 16
3.2.2 Data analysis trap study ... 18
3.3 Methods of market study ... 20
3.3.1 Data collection ... 20
3.3.2 Data analysis of interviews ... 22
4 Results ... 23
4.1 Results of trap study ... 23
4.2 Results of market study ... 31
5 Conclusions ... 37
6 Discussion ... 38
7 Recommendations ... 40
References ... 43
Appendix I Questionnaire for restaurants or chefs ... i
Appendix II Questionnaire for fishermen ... iii
Appendix III Questionnaire for the general public ... v
Appendix IV Detailed results from post-hoc analysis bycatch and depth ... vii
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1 Introduction
Coral reefs are one of the most biologically diverse and most productive ecosystems on our planet.
Covering less than one percent of the seafloor but still housing 25 percent of all marine life (Kaiser, et al., 2011). Besides the high biological diversity and productivity, coral reefs also provide numerous ecosystem goods and services. Coastal defence, seafood, and recreational activities are only a few examples (Moberg & Folke, 1999). Regarding the Caribbean island of Saba, dive tourism and fisheries are most reliant upon the balanced functioning of the reefs around the island and on the nearby Saba Bank atoll. Dive tourism is on a rise and Saba is being discovered as a unique dive location with stunning reefs and associated biota. Saba fishermen set out on a daily basis to the Saba Bank atoll to haul fish and lobster pots, products of the coral reef ecosystem and stocks of which in the past have been sustainably harvested with a relative steady catch each year (De Graaf, Brunel, Nagelkerke, &
Debrot, 2017).
Global coral reef health has been declining through multiple anthropogenic, and natural causes. This is also the case for the Caribbean Sea. Since 1970, coral cover in this region has declined by 80 percent.
Overfishing, destructive fishing methods, coastal development, sea level rise, ocean acidification, coral bleaching and other diseases, and invasive species are all examples of threats to coral reef health (van der Vlugt, 2016).
Invasive species pose a threat to other native species and are known to disrupt the balance of an ecosystem. The lionfish (mainly Pterois volitans and in lesser amounts Pterois miles) is an invasive species which are believed to have invaded the Caribbean Sea after local aquariums or hobbyists from Florida introduced them into the Atlantic Ocean in the late 1980s. Since then they have been spreading throughout the Atlantic, the Caribbean Sea and the Gulf of Mexico as can be seen in Figure 1 (Schofield, 2009; Ocean Support Foundation, 2019).
Lionfish are particularly hard to control for multiple reasons. Lionfish are non-native to the Caribbean Sea and have virtually no natural predators to control their populations in this region (Albins & Hixon, 2013). They reach sexual maturity within their first year and can produce up to 15.000 eggs every four days throughout the whole year. Additionally, they can tolerate a wide variety of habitat conditions (Zaima, 2015).
They have no specific preference for prey species and possess a huge appetite which seems to be never stilled. On reefs, they target juvenile reef fish and reef grazers, as well as crustaceans (Meesters
& Becking, 2017). This leads to a reduction of ecologically important species like parrotfish which, for example, are known to keep reef-smothering algae at a minimum. Furthermore, lionfish reduce recruitment rates of important reef fish (Albins & Hixon, 2008; Zaima, 2015), and their predation on juveniles also heavily diminishes commercially important fish stocks (Green, Akins, Maljkovic, & Côté, 2012).
In 2009 a lionfish was spotted for the first time in the waters of Saba. It Is thought that lionfish started to settle the Saba Bank during the next two years and its presence was fully rooted around 2011.
Considering biodiversity, the Saba Bank is a unique ecosystem in a relative healthy state, accompanied by high productivity and biodiversity (Meesters, Bijkamp, & Bijvoet, 1996). The Saba Bank is home to many species of fish, corals, sponges and macro algae (Toller, Debrot, Vermeij, & Hoetjes, 2010;
Williams, et al., 2010; Van Beek & Meesters, 2014; Van Der Vlugt, 2016;). The waters are mostly oligotrophic, and this is favourable for the existence of open water reefs. The corals of the Saba Bank are in a relative healthy state and provide an essential area for fish to reproduce. The Saba Bank’s rare relatively pristine state is partly due to its remote location. These features contribute to the Saba Bank
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being an important area for fisheries for many years, fisheries which mainly focus on the West-Indian Spiny Lobster (Panulires argus) and deep-water snappers collectively known as redfish.
Lionfish now regularly shows up as bycatch in the redfish fisheries of Saba. In the past fishermen would feed the sharks with their caught lionfish but over the years a growing consciousness about the edibility of lionfish has led to a demand from some restaurants for
lionfish meat (Kuramae Izioka, 2018). Now, most fishermen sell their lionfish. However, selling prices are relatively low and latest estimates put the price at about three to four dollar per pound of uncleaned lionfish (Kuramae Izioka, 2018). This is mainly because the catch rate varies so substantially, and no steady supply can be realized. Fishermen don’t selectively fish for lionfish and lionfish abundance and distribution on the Saba Bank is as of now still largely unknown. The only pattern which is known now, is that lionfish tend to show up more often in the deeper deployed fish pots and lesser so in the shallower lobster pots, indicating a preference for deeper waters. Still, most fishermen keep the lionfish they have caught to sell them to a few restaurants which have shown interest in preparing and serving it when available.
In 2017 the fishermen and the Saba Conservation Foundation came to an agreement to close the redfish fisheries for a period of six months due to declining fish stocks and allow for recovery of the fish stocks. Since then, some fishermen have shown interest in commercially fishing for lionfish, especially when it could serve as an alternative for red fish fisheries during a future closed season (De Graaf, Brunel, Nagelkerke, & Debrot, 2017). Experiments with modified fish traps have been conducted by the Saba Conservation Foundation in cooperation with 7senses and World Wildlife Fund (WWF) Caribbean to explore the possibilities for
Figure 1. The expansion of the lionfish invasion between its first discovery in Florida in 1985 and 2015, when it arrived in the Gulf of Mexico and the Lesser Antilles (Lodge, et al., 2016).
Figure 2. A typical chevron-shaped fish trap with the single entrance funnel at the base. Attached is a long line, usually twice or three times the intended fishing depth to avoid drifting of the trap. A door is installed on the other side to allow for emptying of the trap’s contents (Slack- Smith, 2001).
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selective trapping of lionfish on the Saba Bank in attempt to offer a lucrative solution to the problem.
In order to appeal to fishermen, these modifications required little reworking and made use of the same materials fishermen use for their own pots. The project was extended the next year with funding from WWF Caribbean and supported by the Dutch Ministry of Economic Affairs, the Saba Bank Management Unit and Wageningen Marine Research. It now aims to develop designs and do trials with modified fishing gear to catch lionfish selectively and to research the possible supply chain and market for lionfish to make such a fishery appeal to fishermen financially. Such a project adheres to recommendations given by Debrot & van den Burg (2019) to start experimenting with trapping lionfish. Whether lionfish can be caught selectively using fish traps remains largely unknown and a large-scale trap study performed in Bermuda is the only source of information on this subject and made use of many different designs of altered lobster pots (Pitt & Trott, 2015).
Most of Saba’s fishermen prefer to use traps shaped like a chevron, that is why they are also called
‘’swallow tail’’ or ‘’arrowhead’’ (see Figure 2). These types of designs are found throughout the Caribbean (De Graaf, Brunel, Nagelkerke, & Debrot, 2017). They have been proved to be one of the most effective designs for commercially interesting fish species (Dalzeli & Aini, 1987; Collins, 1990).
The modifications used in the lionfish trap experiments done earlier are based on this this design. The most important difference is the use of an artificial fish aggregation device (FAD). A FAD is permanent or semi-permanent man-made structure used to lure certain target species to a specific location, most commonly to be able to catch them in either pots or trawling (Food and Agriculture Organization of
the United Nations, 2019). In the modifications it is represented by a plastic crate with holes cut into its side, instead of organic bait. The first modification is a regular traditional fish trap, except it has a FAD placed inside. The second modification is also a traditional trap but with three extra funnels attached to it on the inside along with the FAD (Figure 3).
Figure 3. Overview of the two modifications of the classical arrowhead fish trap design.
Pictures A and B represent a traditional design, and, in this case, carry an orange FAD.
Pictures C and D represent a funnel trap design having three escape funnels built into its sides. This trap possesses a blue FAD. On pictures A and D, the main door can be seen having biological degradable ropes as hinges.
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These funnels aim to diminish bycatch and prevent aggregation of lionfish around the trap. Chapter 3.2 will continue with a more elaborate explanation about the FAD and the methods of trap construction.
Problem description
Corals and fish populations, such as the redfish, have been declining in the last couple of years (De Graaf, Brunel, Nagelkerke, & Debrot, 2017). Redfish are a main target for Saban fishermen and a decline in their populations has been noticed in recent years by fishermen as well (Anonymous fishermen, pers. communication, August 2019). In the recent past, this has led to the agreement between the Saba Conservation Foundation and the fishermen of Saba to close the redfish fisheries for a period of six months (April 1st 2017 – September 30th 2017), to allow the redfish stocks to recover (Eelderink, 2016). Such closed seasons for redfish may return in the future, which will result in an income loss for the fishermen. To compensate the loss of income, possibilities for commercially targeting lionfish need to be investigated.
As of now, lionfish sells for only half as much per pound as redfish does, and due to lack of selective lionfish trapping gear, a lionfish fishery in for now not an adequate substitute during a closed redfish season. It is known that demand is increasing as knowledge becomes more widespread that the fish is a delicacy and safe to eat, however, the demand for lionfish is still unstable, as only one restaurant on Saba has lionfish permanently on the menu, while others serve it regularly as special or as catch of the day. It is suspected that demand of lionfish is currently higher than the supply can deliver, however, clear data to verify this suspicion is lacking.
Problem statement
Information about the effectiveness of different lionfish trapping methods for usage on the Saba Bank is still absent. Furthermore, it is unknown if a commercial market for lionfish on Saba can be profitable for Saban fishermen.
Research aim
This research aims to test the effectiveness of two different methods of lionfish trapping.
Additionally, it aims to give an approximation of the feasibility of a potential commercial lionfish fishery using the most effective lionfish trap method.
Research question:
Which lionfish trapping method is the most effective for targeting lionfish on the Saba Bank, and is a lionfish fishery with its associated bycatch a feasible alternative for Saba’s fishermen during a closed season for redfish fisheries?
To operationalize the main research question multiple sub questions were developed:
Sub-question 1:
Which method of lionfish trapping is the most effective for targeting lionfish on the Saba Bank?
Sub-question 2:
Is selectively fishing for and selling of lionfish and associated bycatch an economically feasible option for Saban fishermen?
The next chapter will give a more detailed description on the methods on how these questions will be answered.
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2 Background information
To provide background information on the most important concepts of this research, this chapter describes the basic description of lionfish biology and ecology, a description of the Saba Bank fisheries and associated policy and the history and current state of lionfish awareness and eradication programs in the wider Caribbean area.
2.1 Description of lionfish biology
The two most commonly knowsspecies in the lionfish (Pterois) genus are the P. miles and the P. volitans (see Figure 4). ‘’Pterois’’ has its origin in the Greek word for ‘’feathered’’.
‘’Miles’’ has its origin in the Latin word for ‘’soldier’’ and ‘’volitans’’ is again Greek, meaning ‘’flying’’.
Although two separate species, they appear similar. The only obvious difference is found within the number of dorsal and anal fin rays.
The P. miles has ten dorsal and six anal fin rays and the P. volitans has eleven and seven respectively (Schultz, 1986).
Lionfish are native to the Indo-Pacific
region. P. miles mainly occupies the Indian Ocean and the Red Sea area while the P. volitans is more focussed in the pacific region and Australia (Schultz, 1986; Schofield, 2009). Since the early nineties of the twentieth century the two species have been introduced to the Western Atlantic and Caribbean regions (Biggs, 2009). They are described as passive hunters, relying heavily on their camouflage with bands of red, white and creamy colours covering its body. They have got prominent pectoral fins, used as wide fans to corner their prey. Asides from being ferocious predators with capabilities to eat almost any organism smaller than them they also resist being predated upon by possessing multiple venomous spines on their dorsal, pelvic and anal fins, numbering up to 18 in total (Bellis, et al., 2012).
However not lethal, contact with these spines causes serious injury and discomfort to humans. This feature is part of the reason why the consumption of lionfish is still looked upon suspiciously.
2.2 Description of Saba bank fisheries
About eight to ten fishing vessels are active on Saba, supporting about 30 people directly with employment and income (Toller & Lundvall, 2008; De Graaf, Brunel, Nagelkerke, & Debrot, 2017). The two main fisheries on Saba are both trap-based, one focusses on the West-Indian spiny lobster and the other on deep-water redfish, mainly consisting of snapper species such as blackfin (Lutjanus buccanella), yellow-eye (Lutjanus vivanus) and the vermillion snappers (Rhomboplites aurorubens) and the grouper red hind (Epinephelus guttatus) (see Figure 5) (Toller & Lundvall, 2008). Most fishermen practise both types of fisheries and have their own traps. Lobster traps are deployed in the shallow flats of the bank, and often catch a diverse variety of smaller reef fish species as well. The
Figure 4. Lionfish external anatomy (Rolling Harbour, 2019).
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redfish traps are deployed on the deeper slopes of the bank. For lobster fisheries the main type of bait used are pieces of cowhide. To enhance aggregation, fishermen tend to leave one lobster in the trap when it is redeployed again. In redfish fisheries, most fishermen use Cololabis saira, or as it is commonly referred to, ‘’Japanese bait’’ imported from Taiwan, as well as pieces of undesired bycatch saved from previous fishing trips for this purpose.
Lionfish has been reported as bycatch in the recent years, especially in the deeper redfish traps. It amounts to about 1 lionfish per 1 to 2 redfish traps hauled (De Graaf, Brunel, Nagelkerke, & Debrot, 2017). However, from time to time huge numbers of lionfish are being caught on a single fishing trip, while at the same time days can go by when none are caught whatsoever (Anonymous fishermen, pers. communication, July 2019).
The lobster fishery is the most economically significant. Around 2008, approximately 0,84 lobsters were caught per trap-haul and a total of 83 kilograms per trip with a total value of $1.3 million a year.
Bycatch of smaller reef fish amounted to $68.700 per year (Toller & Lundvall, 2008). According to De Graaf, Brunel, Nagelkerke, & Debrot (2017), there have been no signs of overfishing. Redfish fisheries haul approximately 4,5 kilograms of per trap-haul and 132 kilograms of redfish per trip. Bycatch amounts to approximately 12 kilograms a trip. The value of the redfish is about $289.000 a year. The bycatch value a year amounts to $15.502 a year. The fleet makes an avergae of 3,7 fishing trips per day, which amounts to a projected 312 fishing trips a year for redfish (Toller & Lundvall, 2008).
For the sake of sustaining healthy fish and lobster stocks Saba’s fisheries are being monitored continiously. Monitoring happens through various methods, such as daily short interviews with the fishermen to assess their daily catch, area of fishing and methods of fishing. Size measurements of the catch and inventarisation of the species composition happen on a weekly basis. The most extensive form of monitoring takes place on board of the fishermen’s vessels where all catch is measured and recorded while the fishermen haul their traps. The advantage of this type of monitoring is that even immediately discarded bycatch can be measured and recorded, resulting in a full catch measurement.
2.3 Lionfish eradication programs in the Caribbean
One example of how other islands deal with the lionfish invasion is found in the southern Caribbean, on the island of Bonaire. Bonaire has developed their own lionfish eradication program, which has been adopted by the neighbouring island of Curacao two years later. Bonaire started to prepare
Figure 5. The four species usually referred to as ‘’redfish’’ and which show up most in the redfish pots. From A to D:: yellow- eye snapper (L. vivanus), red hind (E. guttatus), blackfin snapper (L. buccanella) and vermillion snapper (R. aurorubens) (Williams J. , et al., 2013a); (Willams, et al., 2013b); (Williams J. T., et al., 2013c); (Patil, 2019).
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already in 2009 before the actual arrival, which was in 2010. A new spear fishing legislation was passed on in 2010 and, with proper training, volunteers, dive operators, scientists and residents started to participate in the lionfish eradication (Carballo-Cárdenas & Tobi, 2016). Comparisons between fished and unfished areas revealed a significant difference in lionfish density (De León, et al., 2013). Lionfish, however, persist not only in the shallows where the limited depths allow for scuba divers to practice spear fishing. A lot of deeper areas further from the shore are left untouched by spear fisheries.
Lionfish is being consumed on Bonaire on a small scale and consumption is promoted, especially to ensure continuation and expansion of the spear fishing program (Albins & Hixon, 2013).
Other islands have also put effort into lionfish hunting and have tried to combine this with consumption. The Bahamas and Bermuda had programs in 2005 and 2006 in which fishers, both recreational and commercial, were trained in spearing lionfish (Wilms, 2015). The short-term results were positive, but in the long-term a continuing dedication from individual spear fishers is required and that tends to be problematic (Carballo-Cárdenas & Tobi, 2016).
In 2010 in Belize, in the eastern Caribbean, the immediate response by the authorities was to promote the removal of lionfish by fishermen and dive operators by giving a $25 cash reward for every individual caught (Majil, 2010). Around 2011 a demand did exist among the tourists in Belize for lionfish meat, but no restaurant served it consequently as fishermen were hesitant because a guaranteed market for selling could not be established and buyers needed a reliable supply. What became clear is that a central handling facility was needed to provide support for both suppliers and buyers. When a major buyer appeared from the U.S.A. it gave the confidence to establish a fishing cooperative giving support to buyers and sellers and the Northern Fisherman’s Cooperative began to stockpile lionfish for bulk export. This also resulted in a higher supply of lionfish for local consumption at home and restaurants (Chapman, 2014). A five-steps market-based approach through commercial fishers to control lionfish in Belize was developed afterwards (Blue Ventures, 2017).
In the U.S. Virgin Islands research has shown that consumers are willing to pay for lionfish, especially when they know the environmental concerns surrounding lionfish. Also, the maximum price consumers are willing to pay matches the price fishermen would accept for their catch (Simnitt, House, Larkin, Tookes, & Yandle, 2018). A commercial lionfish market seems to be plausible in the U.S. Virgin Islands. The principles of ‘’willingness to pay’’ and ‘’willingness to accept’’ will return later in this report.
An example of an actual trap study like this one is found in Bermuda, where the Department of Environmental Protection has been conducting experiments using modified lobster pots to attempt to catch lionfish selectively (Pitt & Trott, 2015). The researchers tested eight different funnel types and different kind of baits, as well has shading the traps. What they found is that for low relief habitats the structure of the cage alone deemed enough as bait, and using dead bait only increased the amount of bycatch. Escape gaps seems to have significantly decreased bycatch of smaller finfish. Another one of the findings was the importance of identifying lionfish hotpots in getting high catch rates. Asides from the trap study, Davis (2016) investigated the market potential of lionfish in Bermuda, and if consumption of the lionfish is a viable measure to control the population in Bermuda’s waters.
According to the study, which interviews were conducted with the fishermen, consumers and the restaurants, the willingness of the consumers to eat lionfish is present at large, as well as the ability of chefs to prepare the fish. However, no selective lionfish fishery exists yet and restaurants can not and will not sustain a permanent presence of lionfish on the menu. Similar results came from Del Carmen Carrillo-Flota & Aquilar-Perera (2017), who investigated the potential of human consumption of the red lionfish in Quintana Roo, Mexico. All stakeholders they questioned, in this case diver-
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fishermen, restaurant owners and fish consumers, showed high willingness to taste and consume lionfish.
There is currently no lionfish eradication program on Saba. Large-scale spear fisheries are hard to establish due to the rough nature of Saba’s waters and its steep slopes under the sea’s surface.
2.4 Change in attitude towards lionfish consumption
Attitude towards lionfish has been changing substantially since the invasion began, and consumption seems to be a viable option in provide some measure of control on the population. In order to have any measurable effect, the consumption of lionfish must be taking place on a sufficiently large enough scale across a wide range of areas (meaning whole of the Caribbean). This can only be achieved by establishing a market and a complementary supply chain for lionfish which extends further than just the inconsistent catching and selling of lionfish locally.
Problems have existed and still do exist with establishing such a market. Awareness about the seriousness of the lionfish invasion and it associated socio-economic and ecological effects amongst the inhabitants (and potential consumers) of the Caribbean region is important.
Small- and large-scale outreach communication programs across the Caribbean have been carried out in recent years to promote the capture and consumption of lionfish. This is often accompanied by advertisements for a delicacy ready to be discovered and includes workshops on how to safely handle lionfish. The Reef Environmental Education Program (REEF), the National Ocean and Atmospheric Administration (NOAA) and the Gulf and Caribbean Fisheries Institute (GCFI) organized a such a workshop in 2013 to investigate and identify the challenges a large-scale harvest and distribution of lionfish as a mean to control the invasion. The workshop participants concluded that a lionfish market is feasible and should be promoted. Also, local control is effective to mitigate the impacts of invasive lionfish at this scale (Bogdanoff, Akins, & Morris, 2014). Consuming lionfish as an approach to control the species is also supported by its high nutritional value, with n-3 fatty acids values higher than most commonly consumed native marine fish species (Morris, Thomas, Rhyne, Breen, & Akins, 2011).
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3 Materials and methods
3.1 Research area
The Saba Bank is positioned in the north-eastern Caribbean Sea (Latitude: 17° 01' 60.00" N Longitude: -63° 24' 59.99" W), and it is a submerged rectangle-shaped carbonate atoll roughly 2.200 square kilometres in size. It is located about 3 to 5 kilometres Southwest of Saba and about 16 to 19 kilometres West of St. Eustatius. The atoll is a completely submerged platform and lies on average 20 to 30 meters (66-98 feet) underneath the sea surface, and this flat surface is one of the main characteristics of the Saba Bank (see Figure 6 for a map of the bank’s bathymetry). The entire structure itself is raised about 1.000 (3.281 feet) meters above the surrounding seafloor. The south-eastern part of the bank is the shallowest part, and from here towards the north-western it gets steadily deeper.
The east and south-eastern margins have an actively growing coral ridge and the minimum depth here is about 7 to 15 meters (23-49 feet). In the deeper western part, the minimum depth is about 50 meters (164 feet) and there are no signs of growing coral (Macintyre, Kinsman, & German, 1975; Van Der Land, 1977).
Figure 6. A detailed bathymetric map of the Saba Bank with the island of Saba towards to Northeast (encircled) and the Poison Bank on the East side of the bank. The 50 to 250-meter deep outline of the bank can be clearly seen, as well as the shallower eastern side in comparison to the western side (Hannemann, 2012).
Bathymetric map of the Saba Bank research area
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3.2 Methods of trap study
To investigate the research question ‘’ Which method of lionfish trapping is the most effective for targeting lionfish on the Saba Bank?’’, a lionfish trap study was conducted on the Saba Bank between March 2018 and September 2019. This study made use of two trap designs to test which one was most effective for targeting lionfish. The traditional chevron-shaped trap, which hardly required any alteration, and a modification of this design which has three extra funnels attached to its sides. Both designs made use of a plastic crate with holes cut in the sides to serve as a FAD, the specifics of which will be elaborated later. No live or organic bait was used. It was assumed that the structure of the trap in combination with the artificial reef would be enough to lure lionfish. The reason this type of FAD was chosen was to exploit the habit lionfish have to seek out small crevices and hiding spots (Hunt et al., 2019). The use of live bait has been shown before to attract more bycatch while not influencing lionfish catch rate (Pitt & Trott, 2015). The three extra funnels of the funnel trap design measure 15 centimetres in diameter and serve as an escape for smaller reef fish and thus aims to diminish bycatch.
This study used two data sets to investigate which trap design is most effective. Data from 2018 has been made available by the Saba Conservation Foundation and was used to get more data points.
Caution is required when comparing data since the traps used in the 2018 experiments contained a smaller mesh size then the traps in the current study.
Construction of the traps in 2018 happened in March. A total of 25 traps were made with a mesh size for both sides and top and bottom of 1,5 by 1,5-inch (38 mm). During the 2019 data collection the mesh size of the sides of the fish traps had to change from 1.5 by 1.5-inch to a bigger 2 by 2-inch (50 mm) mesh wire due to the high costs of importing 1,5 by 1,5-inch mesh wire from Atlantic and Gulf from Miami. 2 by 2-inch mesh wire can easily and relative inexpensively be imported from Minville Marine SXM from nearby Saint-Martin Unfortunately this supplier only alternative is 1,5 inch by 1-inch and according to the Fisheries Regulations BES 10-10-2010 mesh size cannot be smaller than 1,5-inch.
construction of traps happened in July and August. In total 28 traps were built, fourteen of each design. Both designs were constructed from the same materials using the same techniques and tools.
The basic shape and strength of the trap is provided by a rebar frame. The trap itself was constructed with two different types of vinyl-coated wire mesh. Due to a change in regulations regarding the wire mesh of fish traps, the top and bottom were made from 1,5 by 1,5-inch wire mesh and the sides from 2 by 2-inch wire mesh. In the 2018 data set, the sides of the traps
were also made from 1,5 by 1,5 wire mesh. The sides were attached to the top and bottom parts using galvanized steel hog rings. To match the design fishermen use, electrical wire was used to lock the cage within the rebar frame. Two zinc nodes were attached to the rebar frames to prevent corrosion (Nordic Galvanizers, N.D.). A door was put into the trap to empty the trap from its contents after having soaked for a designated period.
The hinges of the door are made from biodegradable rope to prevent ghost fishing in the case of a lost trap. Ropes were measured with a measuring tape and were attached on the two outer sides of the top of the cage using a clove hitch knot (see Figure 7).
Traps of both designs have the same general dimensions of 153 cm in length, 157 cm in width and 50 cm in height. The main funnel is the same size for both designs as well, with a length of 75 cm and a
Figure 7. Clove hitch knot used to attach the ropes to the trap
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width of 20 cm. The entrance hole has a length of 18 cm. The door is 20 cm in length and 41 cm in Width. Diameter of the funnels is 15 cm.
A FAD was placed in each trap. As seen in Figure 8, in this study the FAD was represented by orange and blue coloured plastic crates used previously for storing and transporting bottles for retail purposes. In each crate a set of randomly sized rectangular holes have been cut. Originally, and in previous experiments conducted by the SCF, only orange coloured crates have been used. Due to the unavailability of the required amount of 28 of these crates, the choice has been made to use similarly shaped blue crates as well to match the required amount. The choice has been made to use an even amount of each type of crate, thus fourteen of each, divided evenly over each trap design. it was thought important to consider the implications of these different coloured and slightly differently shaped crates for the results. It was hypothesized that the colour difference would not matter since both the colours orange and blue would disappears on the depth on which the traps would be deployed (Chaplin, 2019). However, the slightly different shape and size could influence the results and must be considered. Table 1 emphasis the difference in dimensions between the two FAD’s.
Table 1. L x W x H dimensions of the two FAD’s in centimetres.
Orange FAD (in cm) Blue FAD (in cm)
Length 30 34
Width 45 48
Height 38,5 38
Figure 8. The front and side view of the two FAD colour designs used in the experiment during the summer of 2019. Notice the holes cut into the sides to mimic crevices and allow for lionfish to enter.
16 3.2.1 Data collection
From May 2018 until September 2019 modified lionfish traps have been deployed by the Saba Bank Management Unit and hauled on average about once a week. Between the 15th of July and the 15th of August 2019, 28 traps were deployed and hauled on the Saba Bank. It was attempted to deploy one of each trap design, thus four in total, on one line at one specific depth between 60 and 450 feet. This would result in a total of seven lines, of each four traps, over a gradient of increasing depth. This would allow for comparison of trap designs over a depth profile from 60 feet to 450 feet. In practise this method is difficult to apply because of the movement of the vessel during deployment. Graph 1 gives the depth profile on which the two designs have been hauled during the research. The number of traps hauled are not evenly distributed over the fishing depth. Traps have been hauled between a depth of 60 and 450 feet. Most traps were hauled in the range of 151 to 360 feet and less so between 60 and 150 feet and 361 and 450 feet. No traditional traps have been hauled in the depth category of 421-450 feet. Funnel traps have been hauled at every depth category.
Traps were deployed ensuring the top side remains up. Afterwards the rope was quickly uncoiled and continuously fed after the sinking trap. The three buoys on the end of the rope where thrown overboard at the end. Immediately after the deployment of a trap, the time and date of deployment, waypoint, coordinates, trap design, trap number and observers were recorded. In figure 9 a map with the sampling location of the 2019 data set can be found. Figure 10 shows a magnified map of the sampling location with the 7 different lines of traps from 2019. On each line 4 traps were deployed.
Hauling of a trap was done by hand and by a hydraulic winch on separate occasions, depending on the availability of a ship outfitted with such a mechanism. Hauling by hand was done on Queen Beatrix II (SCF’s ship). Hauling with winch was done on Bradley Johnson’s ship, a Saban fisherman. The hauling of a trap by hand is substantially more time and physically intensive than by using a hydraulic winch powered by the vessel’s engine. The technique used to haul a trap by hand is as follows. Once the
Graph 1. Depth distribution of all traditional and funnel traps hauled during the 2019 data collection session. Most traps have been hauled between the depths of 211-240 feet. In total 129 traditional traps and a total of 146 funnel traps have been hauled.
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buoys of a specific trap were located, a large extra buoy was attached to the rope of the trap using a carabiner or shackle. By accelerating the boat for a short while, the buoy slowly slides back on the rope, bringing the trap up to the surface and allowing for a person to haul the slack of the rope in by hand. When the rope has been pulled in and the buoy has been brought back to the boat, the rope is tightly secured to the cleat and the processes of accelerating starts over again. The buoy moves backward, the engine is reversed, the rope unwounded and pulled in again. After a couple repetitions of this process the trap reached the surface and was hauled on board by two persons. The door was opened, and the catch unloaded in a tray. Lionfish and bycatch were recorded and measured. In total 75 traps were hauled in 2019. In 2018 a total of 183 traps were hauled.
After the measurements were taken and bycatch and lionfish where either thrown overboard or kept for further analysis on shore, the trap would be quickly but thoroughly inspected for defects. These could be missing zinc nodes, loosened cable zip ties, broken ropes for the door, missing tag numbers, and broken hog rings. After emptying the traps, they were deployed again at the same depth.
Risk analysis
Fishing on the Saba Bank is not without risks. The bank is known for its rough seas and rapidly changing currents and weather conditions. One must consider that it might not be possible or responsible to set out at any time and changes have been bade in scheduling fieldwork dates. This may have and has
Figure 9. Location of sampling Figure 10. Magnification of sampling location with the 7 different lines of traps. On each line 4 traps were deployed.
Map of sampling points Map of sampling location
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had consequences for the research, as the soaking time of seven days which was aimed for may not always have been realized. Another problem which arises due to the Saba Bank’s characteristics is the potential to lose fish traps, either by simply not being able to find the buoys or because the trap has been set adrift by rough underwater currents and may be lost forever and will thus start contributing to ghost fishing. If traps couldn’t be found during a trip, it may have been found again on the next trip likely doubling the soaking time. The depth meter used during fieldwork on the Queen Beatrix II (research vessel) did not always function properly and gave inaccurate estimations. Traps may not always have been deployed on the depth which they were planned for. Most important was to write down the depth accurately each time the trap is hauled and make sure it was accounted for during statistics.
Another contributing factor during the data collection phase was that traps have been stolen by most probably by another fisherman or fishermen. The trap is hauled and emptied and thrown back again.
Evidence for trap stealing is the cable zip tie being cut off from the door or a different style of knotting the electrical wire into the frame to lock the door. Unfortunately, this happened a few times and measures to at least be able to observe evidence have been put in place only during the last phases of data collection. This made it unable to tell exactly how many traps have been stolen and to what extend the data may be flawed. It does not necessarily mean that the stolen trap is hauled empty as new batch of fish may have been caught in the trap in the meantime.
3.2.2 Data analysis trap study
After collection of data, the data was processed into Microsoft Excel 2016 data sheets. The data from the excel sheets was then transferred into IBM SPSS Statistics 26 for statistical testing. Several datasets have been produced. One for the sample session of 2019 and one which has bulked together the data for both 2018 and 2019, one for lionfish size data, one for bycatch species count and size data. The bycatch species count, and composition dataset has been filtered in such a way that all species which comprised less than 1% of the total caught individuals were left out. This way a more significant overview can be given of the catch variety and most important bycatch species. The reason datasets have been divided between 2019 and 2018-2019 was to take in to account any possible differences in results which might be due to the difference in mesh sizes or the colour of the FAD. The other two datasets are combined data from both 2018 and 2019. The variable ‘’depth’’ has been visually binned for all datasets to create categories to allow for better comparisons between frequencies over a depth gradient. Thirteen categories have been created with a split at every 30 feet. The first category
Table 1. Data and variables of the four datasets used in analysis. Top left is the 2019 dataset, top right the combined 2018-2019 dataset, bottom left the bycatch data and bottom right the lionfish size data.
Table 2. Overview of the different datasets and associated variables and their unit of measurement.
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(shallowest) goes from 60-90 feet and the last category (deepest) goes from 420-450 feet. Table 2 gives an overview of the different variables for all datasets as they were used in analysis in IBM SPSS.
A Shapiro-Wilk test (Shapiro & Wilk, 1965) was used to investigate if the data was normally distributed for the 2019 and 2018-2019 datasets. Because the assumption of normal distribution was not met for the variables Number of lionfish (p = 0,000), Number of bycatch (p = 0,000), and number of bycatch species (p = 0,000) for the 2019 dataset, it was decided to use non-parametric tests to test for any significant differences. All test had an a-priori significance level of 0.05. Similar results came from the 2018-2019 dataset. The assumption of normal distribution was not met either for the variables Number of lionfish (p = 0,000), Number of bycatch (p = 0,000), and number of bycatch species (p = 0,000).
The new data from 2019 was analysed first. The significance of the FAD colour in relation to lionfish and bycatch rate was analysed at the start. Hypothesized was that the different colours would not influence the catch rate of lionfish or bycatch. Because no statistical significant differences could be found using a Mann-Whitney non-parametric test between FAD colour and the number of lionfish, the number of bycatch, and the number of species, it was decided to not take FAD colour into account and to combine the 2018 and 2019 data to get more data points.
The following analysis were carried out with the combined 2018-2019 dataset It is important to note that when this data was analysed the FAD colour was no longer considered and assumed to have no influence on the variables analysed. The decision was made to discard mesh size in the analysis all together and focus purely on the differences between the two to trap designs. If a difference can be found between the mesh size and the amount of lionfish, bycatch or bycatch individuals, it does not tell whether the difference is in fact due to the difference in mesh size. By combining the datasets and eliminating the mesh size variable the n-values increase significantly in size.
Mann-Whitney U non-parametric tests and Kruskal-Wallis H non-parametric tests (Mann & Whitney, 1947; Kruskal & Wallis, 1952) were performed to investigate possible differences between the lionfish catch rates and amount of bycatch for both trap designs and the influence of fishing depth on the amount of lionfish, bycatch and bycatch species caught. Significant results between lionfish catch rate and associated bycatch over trap designs does give a satisfactory answer as to which method works most desirable. Significant results about fishing depths in relation to amount of bycatch species and individuals and lionfish allow for recommendations in combination with the most effective trap design.
As a complementary tool, scoring system has been developed to rank all individual hauls based on their content of lionfish and amount of bycatch. A score from one to ten was given to each trap haul.
Ten being the highest score and one being the lowest. This score is based upon two separate scores, on based on the amount of lionfish and one on the amount of bycatch. A scale was created containing six categories lionfish and 5 categories for bycatch amount per single trap haul (see Table 3). Since the maximum amount of lionfish caught in a single trip in this study was nine, the category ‘’9-10’’ was given the highest score of 5. Since the maximum amount of bycatch in a single trap in the study was 50, the category ‘’41-50’’ was given the lowest score of 1. After each trap haul has been given two separate grades, they were added in to a singular 1-10 grade. In Table 3 an overview of the scoring system is given. For example, if a trap contained nine individual lionfish and eight individual bycatch fish, the trap will get a score of 10. When a trap would have 0 lionfish and 49 individual bycatch fish the score would be 1. A completely empty trap would still get a score of 5.
After the scores were calculated for every trap. A Shapiro-wilk tests was used to test if the variable
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effectiveness score was normally distributed. The variable effectiveness score however was not normally distributed (P=0.000).
Table 3. Overview of the score categories for assessing the most effective lionfish trapping method.
Number of Lionfish Score Number of bycatches Score
0 0 0-10 5
1-2 1 11-20 4
3-4 2 21-30 3
5-6 3 31-40 2
7-8 4 41-50 1
9-10 5
Because the assumption of normality was not met, a Man-Whitney U nonparametric test was used to test for significant differences between the effectiveness score and the two trap designs. The means of the scores for both trap designs were compared to each other to get a grasp of the effectiveness of both methods. Based upon statistical testing of the different trap designs and their contents, and the results of the scoring system the most efficient trap can be determined.
3.3 Methods of market study
To answer the question ‘’ is selectively fishing for and selling of lionfish and associated bycatch an economically feasible option for Saba’s fishermen?’’, three separate questionnaires conducted with three population groups. One with the fisherman of Saba, one with the restaurant owners and chefs of Saba, and an online survey which aimed the target the consumers and local population of Saba. The three questionnaires can be found in Appendices I, II, and III. Davis (2016) used questionnaires for the same three groups of general public, restaurant chefs and fishermen on the island of Bermuda for his research regarding the possibilites of a commercial lionfish market in that region, and his methods were partly copied in this study. Although in theory the method of self-completion questionnaires was used instead of face-to-face interviews, it often happened that questionnaires were read-out loud for the respondents to answer. This would often results in a mixture between an interview and a true self- completion questionnaire, as often the motives behind certain choices in answers were given.
Although these motives and discussion points are not taken in to account in the analysis of the questionnaire results, they do provide interesting perspectives to be further reviewed when answering the sub- and main questions and discussing the results. Overall, questionnaires were structured, and the results were kept anonymous to be able to compare data between respondents and to limit socially desirable answers.
3.3.1 Data collection
Questionnaires for restaurant owners and chefs
Restaurants on the island were visited during one week in September. The reason for the visit would be explained to whomever would come to say welcome. Sometimes this would be the owner, otherwise the owner would come to speak when asked for. In some cases, the owner was also the head chef of the restaurant. The owner or head chef was explained the purpose of the research and the structure of the questionnaire. It was preferred to carry out the questionnaires in person to allow for more in-depth discussion regarding certain aspects, but this was not always possible due to the busy schedules of the owners or chefs. In this case the questionnaire would be given to them to fill out in their own time, and an appointment would be made to retrieve the filled-out questionnaire on another day.
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In total eleven restaurants were approached. Not a single restaurant refused to participate. Most restaurants were in the village of Windwardside. Three were in The Bottom and two were located down in the harbour known as Fort Bay. Most owners or chefs were happy to help with the questionnaires, while some were a little reluctant at first. The aim was to keep all results anonymously, the respondents have been given a unique survey ID, reaching from R1 (R as in ‘’Restaurant’’) to R11 (see Table 4 for an overview of the surveys, location and role of the respondent). The restaurants had a wide variety of styles, ranging from simple non-formal diners and bars, to the classic semi-formal grill and pizza places to more luxurious and chic restaurants with extensive menus. Reluctance from two from the eleven respondents was either due to lack of interest and knowledge about lionfish or since the owner aimed to create a vegetarian and vegan menu and was not interested in extensively discussing lionfish. Both of these questionnaires were taken on the spot.
Table 4. Overview of the restaurants which were part of the survey. Information is given on the location of the restaurant, whether the main respondent was either the owner, head chef, or both and if the questionnaire was self-completed entirely or taken on the spot.
Survey ID Location Role of respondent Self-completion or
taken on the spot
R1 Fort Bay Owner and chef On the spot
R2 Windwardside Owner and chef Self-completion
R3 Windwardside Owner Self-completion
R4 Fort Bay Owner Self-completion
R5 The Bottom Owner and chef On the spot
R6 Windwardside Owner Self-completion
R7 Windwardside Owner and chef Self-completion
R8 Windwardside Chef On the spot
R9 The Bottom Owner and chef On the spot
R10 Windwardside Owner On the spot
R11 The Bottom Chef On the spot
The focus in the questionnaires for the restaurant owners and chefs was on their knowledge, or lack of, lionfish and its preparation, their possible interest in serving lionfish and associated willingness to pay (WTP) for a pound of uncleaned lionfish, their willingness to accept (WTA) for a dish with lionfish, and the demand for lionfish they experience from customers in their establishment. Willingness to accept (WTA) and willingness to pay (WTP) are terms often used in market studies. WTA is the minimum amount of money a person is willing to accept for a product or service. WTP is the maximum amount of money a person is willing to pay for that product or service (Martin-Fernández, et al., 2010).
Information on these topics will aid in mapping the potential market and supply chain for caught lionfish and its value.
Questionnaires for fishermen of Saba
Fishermen on Saba are obligated to participate in any research in relation to the Saba Bank. In total five fishermen where approached for the questionnaire. It was helpful that the fishermen were already known personally through the fisheries monitoring project of Wageningen Marine Research.
The questionnaires and the research purpose were introduced beforehand to the fishermen in person whenever they would arrive in the harbour after a fishing trip. They were asked if they would have time somewhere in the coming days to fill in the questionnaire. A positive answer to this question was given most of the time, although it was met with some reluctance by some. The fishermen would thus be approached again on another day after they would return, and the questionnaire would be given to them and conducted with them on the spot, with the questions and answers read-out loud. This
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personal approach was fruitful for a bit of discussion between the questions and gives a bit more insights into the fishermen’s motives for giving certain answers. This also may have contributed to more honest answers as we were aware that some fishermen had a lack of faith in the experiment with the lionfish traps and the methods used and tended to disregard any notion of selectively fishing for lionfish. To ensure the animosity of the fishermen and their answers each questionnaire was given a unique survey ID, reaching from F1 (F as in ‘’fisherman’’) to F5. The focus in the questionnaires for the fisherman was on potential buyers of lionfish, possible export locations, the demand for lionfish meat on Saba and the fishermen’s WTA per pound of lionfish in US Dollars. Based on a hypothetical example of a nine-hour fishing trip, which is the average duration of a fishing trip according to Toller
& Lundvall (2008), the cost of an average fishing trip was identified. Answers to these types of questions allow for the creation of a hypothetical situation in which lionfish is the main target species, and in turn serves as a basis to calculate the potential of a lionfish fishery in combination with the results from the other interviews and the trap study described earlier.
Online survey general public
To sample the general public an online survey was created using the software from Survey Hero. The survey was distributed using mainly the social media outlet of Facebook. The survey was distributed both to friends and family and it was distributed on popular community pages, including one purely consisting of temporary and permanent residents on Saba. This way it was attempted to sample a wide range of different people with different backgrounds. Also, this method would result in three population groups, those who are residents on Saba, those who have visited Saba either as a tourist or other reasons and those who have not been to Saba. The online survey for the general public investigated if the public knew about lionfish, if they would be willing to eat lionfish, if they knew how to prepare lionfish, and their WTP for a lionfish dish in a restaurant and for a pound of uncleaned lionfish. Because it is known where the respondents come from and whether they have visited Saba or live there, answers from the survey can be compared between these groups. Differences in awareness of lionfish as an invasive species and its edibility can be found, and an idea can be formed about the attitude towards lionfish consumption and its value on Saba itself. The survey was open for approximately four weeks, and when no new responses were coming in the results were exported and saved.
3.3.2 Data analysis of interviews
Data collected during the interviews was processed into datasheets in Microsoft Excel. Data from the online survey was also exported to IBM SPSS to allow for more specific and in-depth interpretation of the data. The information gathered from these questionnaires will be descriptive in nature due to the low n-values, especially for the populations of fishermen and restaurant chefs and owners. Descriptive statistics in the form of percentages and frequencies were applied to the data sets at first to map the differences between the respondents’ their answers, and with the use of bar charts and histograms interesting results are made visible. Regarding questions concerning the WTP and WTA for either a pound of uncleaned lionfish or a lionfish dish (the latter only applying to the restaurants) the mean amounts will be calculated to allow for comparison between groups.
Estimation of economic value of a lionfish fishery
Combining the results of both sub-questions an estimation of the economic value of a lionfish fishery using the most effective method can be made. Using the date on the mean catch rate of lionfish and commercially attractive bycatch species and the mean WTP and WTA for a pound of lionfish combined with the established price for a pound of redfish (Toller & Lundvall, 2008), the total value of a single average lionfish fishing trip can be calculated. Subtracting the mean operational costs for such a fishing trip result in an estimated net-income. However, these are assumptions based upon means. It could
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Figure 11. Lionfish specimen caught in a traditional lionfish trap with a blue FAD. Notice how it resides inside the FAD.
give insights if a lionfsh fishery is able to compare economically to a redfish fishery and if it will thus suffice as an alternative.
4 Results
Firstly, the results of the lionfish trap study will be described followed by the results from the market study.
4.1 Results of trap study
During the whole 2018-2019 period, a total number of 28 trips have been undertaken to the Saba Bank to either deploy traps, haul them or both. In total 275 hauls were done and a total of 182 lionfish have been caught. Most effort has been done in 2018, as nearly twice as much trap were hauled during almost thrice as many fishing trips to the Saba Bank. In total 129 traditional traps have been hauled and 146 funnel traps have been hauled, regardless of FAD colour. A higher number of lionfish have been caught during 2018 (166) than in 2019 (16). Another interesting difference is the amount of trap which have been hauled empty. 7 out of 183 have been hauled empty in 2018 against 13 out of 92 in 2019. Table 5 gives a descriptive overview of the efforts and the catch rates of lionfish and bycatch during the research, with a distinction made between 2018 and 2019.
Table 5. Descriptive data and frequencies of the 2018 and 2019 data collection sessions
2018 2019 Total
Number of trips 21 7 28
Traps hauled 183 92 275
Traditional traps hauled 79 50 129
Funnel traps hauled 104 42 146
Amount of lionfish caught 166 16 182
Amount of bycatch caught 1758 540 2298
Number of traps hauled empty 7 13 20
Average soaking time in days 9,2 10,1 9,5
Trap design and number of lionfish
No significant differences were found between the number of lionfish and trap design (P=0.105).
Although not significant, the mean number of lionfish in the funnel trap tended to be lower in the funnel trap than in the traditional trap design. The traditional trap had an average of 0,82 lionfish per trap while the funnel trap had an average of 0,52. The highest amount of lionfish caught in a single trap haul was nine, the trap design was traditional, and it soaked for 21 days. The second and third highest amounts were eight and seven and both hauls were done using the funnel trap design and soaked for seven days each. Out of the 275 total trap hauls 63 contained at least one lionfish. Only 6 of these traps were hauled in 2019 and the other 57 in 2018 (see Figure for a lionfish caught in a traditional design lionfish trap).
24 Trap design and number of bycatch and bycatch species
The Mann-Whitney U nonparametric test found a significant difference between the two trap designs and the number of bycatch (P = 0,000). Graph 2 shows the mean number of bycatch individuals per trap design. The traditional design had an average of 12,38 individuals of bycatch per trap haul. The funnel design had an average of 4,71 individuals of bycatch per trap haul.
Another significant difference was found between the two trap designs and the number of bycatch species (P=0,000). Graph 3 shows the difference between the mean number of bycatch species and the two different trap designs. The traditional trap design had an average of 3,98 bycatch species per trap. The funnel trap design had an average of 2,52 bycatch species per trap.
Graph 2. Bar chart showing the mean number of bycatch caught per trap design.
Graph 3. Bar chart showing the mean number of bycatch species per trap design
25 Depth categories and number of lionfish
The Kruskal-Wallis H nonparametric test found no significant differences between the depth categories and the number of lionfish (P=0,079). Although no significant difference was found, results show that the depth distribution of caught lionfish closely resembles the depth distribution of the trap hauls (see Graph 1 in methods).
Depth categories and number of bycatches and bycatch species
A significant difference was found between the depth categories and the number of bycatch (P = 0,000). Graph 4 shows the mean number of bycatch per depth category divided over trap design.
Another significant difference was found between the depth categories and the number of bycatch species (P=0,007). Graph 5 shows the mean number of bycatch species per depth category divided over trap design. Post-hoc analysis of the Kruskal-Wallis H test results revealed multpiple significant differences between many depth categories and number of bycatch individuals and species. An overview of all signifcant differences and associated P-values can be found in Appendix IV.
The bar-charts have put both bycatch variables per depth category and observed was a clear decline in both the number of bycatch individuals and the number of species as fishing depth increases. On average, most bycatch species and bycatch individuals have been caught at a depth of 121 to 150 feet.
A distinction between trap design was also made to emphasize the significance possible difference in catch rates on certain depths. What can be seen is that for the mean number of bycatch individuals decreases between 301 feet and 390 feet when using the funnel design, while it increases when using the traditional design (Graph 4). The exact same pattern can be seen when comparing the fluctuations of the mean amount of bycatch species per trap design on the same depth of 301-390 feet (Graph 5).
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Graph 4. Clustered bar chart of mean number of bycatch per depth category divided over trap design..
Graph 5. Clustered bar chart for mean number of bycatch species per depth category divided over trap design.
27 Bycatch composition
During the research a wide variety of bycatch species have been caught. These range from smaller reef fishes like surgeon fishes, butterfly fishes, and cowfishes to larger species such as snappers, groupers and jacks. Table 6 and Graph 6 show an overview of the most common caught species of bycatch during the 2018-2019 study. As mentioned before only bycatch species who represented more than one percent of the dataset were taken into account. The total frequency per species and the percentage of the total amount were recorded. By far the most frequent bycatch species is the blackfin snapper (L. bucanella) with 1011 individuals (46,9% of total). The blackfin snapper is accompanied by other snapper species yellow-eye snapper (S. ruberrimus) with 249 individuals (11,6%
of total) and the vermillion snapper (R. aurorubens) with 231 individuals (10,7% of total). The red hind (E. auttatus) is the fourth most abundant bycatch species with 191 individuals (8,9% of total).
Interestingly these four species are also the main targets in the redfish fisheries of Saba and are all commercially interesting species and comprise 78,09% of total bycatch The longspine squirrelfish (H.
rufus) is also highly abundant with 163 individuals (7,6%), however, this species is not commercially interesting and is always discarded immediately by fishermen when caught in fish traps.
Species Latin name Frequency Percentage of total (%)
Banded Butterflyfish Chaetodon striatus 48 2,2
Blackfin Snapper Lutjanus buccanella 1011 46,9
Blue Tang Acanthurus Coeruleus 43 2,0
Coney Grouper Cephalopholis fulva 37 1,7
Red Hind Epinephelus guttatus 191 8,9
Spotted Goatfish Pseudupeneus maculatus 49 2,3 Longspine Squirrelfish Holocentrus rufus 163 7,6 Vermillion Snapper Rhomboplites aurorubens 231 10.7
White Grunt Haemulon plumierii 93 4,3
White-spotted Filefish Cantherhines macrocerus 39 1,8
Yellow-eye Snapper Lutjanus vivanus 249 11,6
Table 6. Frequency of bycatch species caught in traps.
