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, 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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