Fisheries management

Action Plan for Caribbean Spiny Lobster consists of:

• Threats: overfishing, disease, climate change
• Management goals
• Recommendations: management, legislation, enforcement, science and monitoring, stakeholders, networking, information-education
• Gaps: population and catch data not readily available for Dutch Caribbean, weak island legislation, IUCN designation: Caribbean spiney lobster is ‘data deficient'
• General Information: description and biology

Video documentary describing the importance of the Saba Bank as a natural resource for the island of Saba, including underwater footage and interviews with fishermen and managers.

The “spawn-at-least-once” principle suggests that sustainability is secured if fish become vulnerable to commercial gears only after they have spawned. However, some studies suggest that protecting immature fish is not essential to sustainability because extrinsic factors determine both recruitment and stock status. A meta-analysis was conducted to quantify the independent effects of exploitation pattern and exploitation rate on current stock status. The analysis used empirical data for 38 fish stocks of 13 species in the NE Atlantic. Two metrics of exploitation pattern were used and their sensitivity was compared. As expected, exploitation rate had a sig- nificant negative effect on current stock status. Exploitation patterns associated with high proportional fishing mortality of immature fish also had a significant negative effect on current stock status, providing empirical support for the “spawn-at-least-once” principle. When the fishing mortality of immature fish exceeds half that of mature fish, stock status falls below precautionary limits. Our results suggest that a sensitive metric of exploitation pattern could provide useful information about an aspect of exploitation that is cur- rently overlooked by fisheries management regimes that focus primarily on exploitation rate. 

Queen conch (Lobatus gigas) is an important food source and export product for Belize, where extraction is regulated by shell length (SL) and market clean weight (MCW) limits. However, lip thickness (LT) limits are used to manage juvenile mortality and reduce risk of growth overfishing in other countries. Empirical studies suggest relationships between LT and sexual maturity vary spatially and need to be determined locally. This study was conducted to determine the most reliable, easily measurable proxy indicator(s) of maturity and associated target size limits in L. gigas that can effectively restrict harvest of juveniles. Morphological measures (SL, LT, lip width, unprocessed meat weight, MCW, operculum dimensions), gonadosomatic index (GSI) and histological evaluations were recorded from L. gigas collected in PHMR before, during, and after the L. gigas closed season. Upon determining Period 2 (during closed season) as the peak reproductive period, relationships between these variables in Period 2 were examined. No relationship was found in males between SL and maturity, and was weak in females, whereas there were significant curvilinear relationships between LT and GSI for both sexes, suggesting urgent need to base size limits on LT not SL. LT at which 50% of the population was mature (LT50) was 15.51 mm for females and 12.33 mm for males, therefore a 16 mm LT limit is recommended. MCW of female L. gigas was also significantly related to GSI, indicating MCW may be an appropriate management tool in conjunction with LT as it can be measured at landing sites whereas shells are usually discarded at sea. However, MCW at which 50% of females were mature (MCW50) was 199 g and many individuals exceeding LT50 had MCW <199 g, suggesting the current 85 g MCW limit is too low to protect juveniles yet 199 g MCW limit would be too high to substitute the recommended LT limit at landing sites. To minimize short-term impacts yet maximize long-term benefits to fishers’ livelihoods, multi-stage adaptive management is recommended that integrates initial catch reductions, followed by introduction of size limits of 16 mm LT, and 150 g MCW. Adjustable LT and MCW limits determined by fishery simulation could later be introduced. 

Morphometric measurements were taken from queen conch (Strombus gigas) from various sections of the Antigua and Barbuda shelf to: 1) ascertain if there were spatial variability regarding morphology; 2) analyse length-weight relationships for various maturation stages; 3) develop statistically valid conversion factors for different levels of processed conch meat; and 4) assess current management regimes (e.g., minimum size / weight). For both juvenile and adult conch, shell length differed significantly among the coastal groupings, p < 0.001. Shell lip thickness, an indicator of the age, was also significantly different among the coasts (p < 0.001), where conch from the north and west coast were significantly older than those from the east or south coast of Antigua (p < 0.001). Significant sexual dimorphism was only detected for adult conch (p < 0.001), with females being 4% larger than their male counterpart. The mean lip thickness for conch collected from commercial fishing trips was 25.0 mm (N = 785, S.D. = 5.5 mm) indicating that divers were targeting an old population however the sex ratio of the allowable catch (minimum weight of 225g) was favouring the harvesting of female conch, X2 (1, N = 711) = 4.26, p < 0.05. Conversion factors differed significantly among maturation stages (juvenile, sub adult, adult and old adult), p < 0.001; hence the use of a single conversion factor to transform processed conch to nominal weight is problematic since conversion factor is dependent on the age structure of the population. These morphological differences require a multifaceted management approach (closed season, protected areas, etc) to ensure the long-term sustainability of the fishery. 

The Indo-Pacific lionfish Pterois volitans is an invasive species that was released along the U.S. Atlantic coast and spread to the Caribbean. Lionfish can inhabit a wide range of depths and they lack predation in their invasive range, leading to a successful invasion into their introduced range. Their large appetite combined with having no predators may pose an ecological threat to the Caribbean coral-reef ecosystem. Pterois volitans invaded Bonaire, Dutch Caribbean in 2009, and the extent of their presence and the impact they have upon the reefs surrounding Bonaire has yet to be investigated. Basic components to managing an invasive species are monitoring their occurrence and controlling their abundance. Around Bonaire, managers and diver volunteers catch and kill P. volitans to control their numbers in an attempt to reduce their negative impacts on the ecosystem. This study investigated the effectiveness of the current management strategy, P. volitans removal, by comparing their densities at frequented hunting sites with no-hunting sites. To achieve this, the densities of P. volitans at eight hunted and less frequented sites were calculated by searching for their presence in 50 x 4 m belt transects at five different depths (6 m, 12 m, 18 m, 24 m, 30 m) at selected sites along the west coast of the island. All P. volitans recorded were categorized into three size classes (small: 0-10 cm, medium: 11-30 cm, large: ≥ 30 cm). The results of this study show no significant differences between the densities of lionfish found at hunted sites (10/ha) compared to less frequented sites (16/ha). This study is the only known effort that attempts to determine the effectiveness of P. volitans removal from invaded areas in Bonaire.

This student research was retrieved from Physis: Journal of Marine Science IX (Spring 2011)19: 64-69 from CIEE Bonaire.

Peer-reviewed PHD dissertation, University of California San Diego.

This dissertation is a multi-disciplinary attempt to understand how coral reef resources can be sustainably managed. I begin by examining the peer-reviewed literature on artisanal reef fisheries, identifying gaps in knowledge, and proposing a set of priority areas for future research. Ecological examinations of trap fishing and gill nets follow. Fish trap bycatch can be dramatically reduced by the inclusion of escape gaps that allow juveniles and narrow-bodied species to escape, although catch of ecologically important herbivores remains high. Gill nets capture the few remaining apex

predators present on Caribbean coral reefs, and as such are unsustainable. The second half of the dissertation is a tripartite presentation of the results of interviews with 177 fishers and 211 professional SCUBA divers on Curaçao and Bonaire. First, I consider whether interviewees' baseline conception of a healthy reef ecosystem is actually a degraded state, and they have a "shifting baseline." Then, I evaluate interviewees' discount rates and present bias, and relate those measures to their preferred management approaches. Lastly, I contemplate how to reconcile ecosystem requirements with stakeholder preferences, and use socioeconomic information to develop a sustainable management plan

Widespread use of minimally selective fish traps has contributed to the overfishing of Caribbean coral reefs. Traps typically target high-value fish such as groupers (Serranidae and Epinephelidae) and snappers (Lutjanidae), but they also have high bycatch of ecologically important herbivores (parrotfish (Scaridae) and surgeonfish (Acanthuridae)) and non-target species. One strategy for reducing this bycatch is to retrofit traps with rectangular escape gaps that allow juveniles and narrow-bodied species to escape; yet the effectiveness of these gaps has not been thoroughly tested. On the shallow reefs of Curaçao, Netherlands Antilles, I compared the catch of traditional Antillean chevron traps (the control) to the catch of traps with short escape gaps (20 × 2.5 cm), traps with tall escape gaps (40 × 2.5 cm), and traps with a panel of large aperture mesh. With data from 190 24-h trap sets, the mean number of fish caught was 11.84 in control traps, 4.88 in short gap traps, 4.43 in tall gap traps, and 0.34 in large mesh traps. Compared to controls, traps with short or tall gaps caught significantly fewer bycatch fish (–74 and –80% respectively), key herbivores (–58 and –50% respectively), and butterflyfish (Chaetodontidae; –90 and –98% respectively). The mean length of captured fish was significantly greater in gap traps because juveniles were able to escape via the gaps. Escape gaps reduce neither the catch of high-value fish, nor the total market value of the catch. Therefore, using escape gaps could make trap fishing more sustainable without reducing fishermen’s revenues.

Abstract:

The white sea urchin, Tripneustes ventricosus, is common in shallow coastal waters of the tropical Atlantic Ocean, and is widely distributed in the Caribbean Sea. The species supports small-scale, commercially important, seasonal fisheries in several islands in the eastern Caribbean including Barbados, Martinique (France) and Saint Lucia, and minor subsistence fisheries in Grenada and Saint Vincent and the Grenadines. However, despite significant management and conservation efforts by some countries, white sea urchin population abundance has declined locally. Understanding the large fluctuations in local population size and implementing sound management practices in the white sea urchin fisheries is critical to the sustainable use of this resource in the future, and would benefit considerably from a sharing of information and management experiences. To this end, this circular has attempted to collate both published and unpublished information on the white sea urchin and its fisheries in the eastern Caribbean and perspectives on past and current management of these fisheries.