coral reef fisheries

Herbivory grazing patterns by parrotfish, family Scaridae, and surgeonfish, family Acanthuridae, were investigated on the leeward side of Bonaire, Netherlands Antilles. Due to overfishing, coral disease, declining water quality and global climate changes, coral reefs worldwide are in danger of undergoing phase shifts from coraldominated to algal-dominated ecosystems (Hughes 2007; Nybakken 2001). When nutrient levels are high, algal communities are highly productive and may outcompete corals (Breeman et al 1994). In healthy coral systems herbivores suppress algal growth and are a key component in preventing phase shifts, thus managing reef resilience (Hughes 2007; Folk and Nystrom 2001). This study measured herbivory rates and bite sizes of several species of coral reef fishes on the island of Bonaire, Netherlands Antilles. These measurements and species density data (Steneck 2005) were used to rank species according to their level of herbivory. The five selected herbivore species were the terminal and initial phase Sparisoma viride (Stoplight Parrotfish), terminal and initial phase Scarus vetula (Queen Parrotfish), terminal phase Scarus taeniopterus (Princess Parrotfish), Acanthurus coeruleus (Blue Tang), and Acanthurus bahanus (Ocean Surgeon). Although Scarus vetula has the highest grazing rate (# bites/min) and largest bite size (cm2 ), this study calculates that Scarus taeniopterus, due to large densities, are the primary consumers of algae in the waters of Bonaire (cm2 /minute/species/100m2 ), followed by Scarus vetula terminal phase and Scarus vetula initial phase. As coral reefs are becoming more algal dominated due to nutrient enrichment, knowledge of herbivore ecology and management of herbivore populations is critical to understanding and protecting these threatened ecosystems.

This student research was retrieved from Physis: Journal of Marine Science III (Spring 2008)19: 49-54 from CIEE Bonaire.

Caribbean coral reef ecosystems are threatened by anthropogenic impacts such as pollution, overfishing, and habitat destruction. In an effort to alleviate these pressures and restore habitat, artificial reefs such as marina breakers, Reef Balls, and mooring blocks have been deployed and consequently colonized by marine species. Many studies have investigated the benthic and fish communities developing on these artificial structures as compared to adjacent natural structures. Results have shown that artificial reefs can successfully be colonized by benthic and pelagic communities but are not always comparable to the associated communities. The purpose of this study was to compare the composition of benthic habitat and the use of this habitat by fish between manmade mooring blocks functioning as artificial reefs and natural coral reefs of Bonaire. Quadrats were used to estimate and compare percent cover of benthic organisms on the top and west faces of mooring blocks versus the top and west faces of physically paired natural reef sites (n = 8). An 8 min visual census was conducted on each face of each site pairing to estimate fish abundance and diversity for those species interacting with the habitat. Results showed greater percent live benthic cover on the natural versus artificial reef. Benthic diversity was highest on the west face of the artificial reef when comparing the interaction of face and reef type, but did not differ significantly between reef types. Fish community diversity also did not differ between reef types. However, the composition of both benthic and reef fish community diversity differed greatly between the natural and artificial reefs. It was found that Montastrea annularis and sponges dominate the natural while the brain corals (Diploria labrinthiformis and Diploria strigosa) dominated the artificial reef. Bicolored damselfish (Stegastes partitus) and brown chromis (Chromis multilineata) were found in the highest densities on the natural reef, while sergeant major (Abudefduf saxatilis) and bluehead wrasse (Thalassoma bifasciatum) were found in the highest densities on the artificial reef. This study provides evidence that placement of artificial reefs does not cause a shift in overall benthic and reef fish community diversity on the natural reef, but may change the composition of this diversity.

This student research was retrieved from Physis: Journal of Marine Science VI (Fall 2009)19: 44-52 from CIEE Bonaire.

Reef fish have a pelagic larval stage and settle onto the reef before transitioning to their juvenile or adult morphologies. Settlement can be dangerous for new recruits and mortality is highest during the first one to two days after settlement. Experiments were conducted to determine the effects of predation and habitat depth on reef fish recruitment. Standard habitat units (SHUs) were created from pieces of Millepora skeleton. Two treatments were created using SHUs. The first contained an SHU placed on the substrate that was open to predation (NC). The second treatment contained an SHU in a wire cage to exclude predators (FC). Two replicates of each treatment were placed in two meters of water and at six meters. New recruits were surveyed twice a week for six weeks (n=11 surveys). SHUs were cleared of recruits and algal growth was removed after each census. Overall recruitment was greater in two meters than six meters of water. Recruitment was also greater in FC treatments than in NC treatments at both two and six meters. Trends in recruit density should not have been observed since recruit censuses were taken as replicates. However, recruitment increased over the course of the experiment, which coincided with the lunar cycle. Seven species of fish were observed over the course of the experiment but only two of these species, the wrasse, Halichoeres bivittatus, and the razorfish, Xyrichtys splendens, were observed at six meters. One species, the pufferfish Canthigaster rostrata, was only observed once.

This student research was retrieved from Physis: Journal of Marine Science XII (Fall 2012)19: 1-8 from CIEE Bonaire.

Coral reef fish exhibit remarkably diverse hunting techniques such as solitary hunting, shadow stalking, nuclear hunting, and hunting in schools of fish. This study examines the differences in feeding rates of the Atlantic Trumpetfish, Aulostomus maculatus, while it utilizes four dissimilar foraging strategies. Observations were completed in Bonaire, Dutch Caribbean while SCUBA diving to record A. maculatus striking at its prey. Feeding rates were calculated from the number of bites at prey during an observation period, in order to rank the strategies. Although consumption of prey was not determined, it is expected that feeding rate will track the number of bites at prey items and is used as a proxy for feeding rate in this study. Solitary foraging was hypothesized to exhibit the highest feeding rate due to its high prevalence on the reef, followed by shadow stalking, nuclear hunting, and hunting in schools. Competition for prey during associations with other fish and rarity of dense aggregations of schooling fish was thought to support the hypothesis. In this study, the feeding rate during solitary foraging was found to be significantly lower than shadow stalking, nuclear hunting, and hunting in schools, which were not significantly different from each other. The results indicate that A. maculatus forage more successfully in groups and exhibit multiple foraging strategies to exploit prey most efficiently. The hunting behavior of A. maculatus affects prey and other associated species, thus understanding this behavior may lead to further knowledge of other predatory fish and interspecific interactions.

This student research was retrieved from Physis: Journal of Marine Science XVI (Fall 2014)19: 1-5 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.