The Effects of Trap Fisheries on the Populations of Caribbean Spiny Lobster and Reef Fish Species at the Saba Bank
The Saba Bank is making a name for itself as one of the world’s marine biodiversity hotspots. Several explorations since the 1980s have uncovered the area’s incredibly rich marine life, prompting the Bank to be declared a National Park in 2010 and designated as a Particularly Sensitive Sea Area (PSSA) by the International Maritime Organisation in 2012. What people are less aware of is that the Bank actually holds great economic importance for nearby islands, notably the island of Saba. Local fishermen have used the area for centuries. Nowadays, as is the case with most of the Caribbean islands, the main fishery on the Bank is for the Caribbean Spiny Lobster (Panulirus argus). Lobsters are typically fished with traps, and the catch is sold to nearby islands, among others St. Maarten.
The decline of spiny lobster populations has become a significant environmental and economic concern within the Caribbean region, with total annual landings in decline since 1995. Although the lobster trap fisheries mainly target lobsters, shallow water reef fish like small groupers are also landed. If not properly managed, trap fisheries like any other type of fishery in the Caribbean may result in over-fishing and biodiversity loss and may even alter the ecosystem structure. Assessing the status of the lobster and reef fish population and the possible impact of the lobster trap fishery on the Saba Bank’s marine life is therefore vital to ensure the protection and sustainable use of the area’s natural resources.
The status of the Saba Bank’s Caribbean Spiny Lobster fishery and its effect on the Bank’s fish stock was the focus of a recent study by MSc Imke van Gerwen (2013). Her study is part of the Fish and Fisheries Research Programme that is being conducted on Saba, St. Eustatius and Bonaire under the supervision of Dr. Martin de Graaf of IMARES and Dr. Leo Nagelkerke of Wageningen University on behalf of the Ministry of Economic Affairs. Van Gerwen collected basic fisheries data throughout 2012 and compared it to similar studies conducted in 2000 and 2007, as well as analysed biologically relevant data such as length frequency of the caught lobsters and reef fish, size at maturity of lobster and species composition of landed and discarded reef fish.
One of the main findings of the study is that the Saba Bank’s spiny lobster population may be showing signs of decline, following a similar trend to the rest of the Caribbean. While the number of lobster traps hauled per fishing trip has increased (from 59 to 80 between 1999 and 2012), the number of lobsters landed per trip has actually decreased (from 83 to 52 between 1999 and 2012). The total catch of lobster was estimated as 62 tonnes in 1999, 92 tons in 2007 and 38 tonnes in 2012. The high catch in 2007 was attributed to the higher number of estimated fishing trips in 2007 (1000) compared to 1999 (650) and 2012 (600). No obvious changes in fishing areas on the Saba Bank were observed during 1999-2012.
Of the 49 reef fish species recorded as landed catch, the most common were grunts (White Grunt, Cottonwick), small groupers (Red Hind, Coney) and Queen Triggerfish. Throughout 2012, eight to ten tonnes of mixed reef fish were landed, and an additional ten tonnes of mixed fish were discarded, mainly consisting of grunts, boxfishes and nurse sharks.
The study does, however, highlight some noteworthy achievements towards a more sustainable lobster fishery on the Saba Bank. A 2000 study of the Bank’s fisheries (Dilrosun, 2000. Monitoring the Saba Bank Fishery) found that there was a high percentage of under-sized and berried (carrying eggs) lobsters in the catch. Nowadays, a number of regulations are in effect, such as the required use of a biodegradable panel in traps to prevent ‘ghost-traps’, the ban on landing berried lobsters, and the establishment of a legal size limit for landed lobsters. This 2013 study found that compliance to these regulations is high as the number of under-sized lobsters in the catch has decreased, and practically no berried lobsters and lobsters in ecdysis (moulting phase) are brought in. Furthermore, the mean size of landed male and female lobster showed that predominantly large, mature lobster are landed, well above the minimum legal size of 95 mm carapace length.
To ensure that fishermen, wholesalers, restaurants and consumers can continue to benefit from harvest of Caribbean Spiny Lobster in a sustainable way without endangering the Bank’s marine life, status of lobster and reef fish populations will be closely monitored, assessment models will be developed to determine the stock status and, if required, additional rules and regulations may be implemented.