Predatory fish

Bioindicator species have been used to determine changes in water quality and the effect of pollution at sites of environmental concern. Increasingly degraded water quality throughout the Caribbean is leading marine park managers and scientists to use bioindicator organisms to rapidly detect differences in water chemistry by determining connections between environmental parameters and changes in reef fish communities. This study sought to determine bioindicator prey species that could provide early detection of changes as a result of anthropogenic activities in the coastal waters of Bonaire, N.A. The effects of these parameters on the density and diversity of reef fish species was compared between 4 sites of “more (MI)” and 4 sites of “less (LI)” anthropogenic impact (200 m from of coastal development, respectively). Fish communities were surveyed using a modified version of the AGRRA methodology during the morning and evening. Two 30x2 m transects at 12 m depth were used at each site to survey both prey and predator fish species. Water chemistry including nutrient, bacterial and sedimentation levels were also analyzed to attempt to determine the factor(s) driving the changes. This study revealed significantly greater densities and a higher diversity of prey and predatory fish species at MI sites versus LI sites during the morning and the evening. The species that was found at greatest densities for both LI and MI sites was Stegastes partitus, with significantly more S. partitus at MI sites during both the morning and evening. Thus, S. partitus may be a possible bioindicator of stressors on the reefs in Bonaire. The use of S. partitus as a bioindicator of anthropogenic stress may help increase the effectiveness of marine management protocols in Bonaire and provide a basis for determining bioindicator species for monitoring coastal water quality throughout the Caribbean. None of the water chemistry parameters studied differed between MI and LI sites, therefore, the driver(s) of the differences in prey species (e.g. S. partitus) may be unaccounted for in this study as a result of time lags in the coral reef ecosystem.

This student research was retrieved from Physis: Journal of Marine Science VII (Spring 2010)19: 12-20 from CIEE Bonaire.

Fish protected areas are increasingly utilized as a means of bolstering existing fish stocks while laying the foundation for healthy future populations. Such areas can promote species abundance, density, total biomass, and fecundity. This project set out to study the effects of FPAs on three reef predators, the graysby (Cephalopholis cruentata), the coney (Cephalopholis fulva) and the great barracuda (Sphyraena barracuda). S. barracuda has a substantially greater range (range of median distance traveled between 0.5 and 8 km) than either of C. cruentata or C. fulva, and has complex range tendencies that include site fidelity along with spawning migrations. Since home range size and response to fish fishing protection are correlated, the effects of FPAs on S. barracuda populations may differ in relation to the effects felt by C. fulva and C. cruentata populations. Using visual sampling methods inside and outside of Bonaire’s FPAs, sightings per unit effort were recorded for all three species to compare how the predators might respond to the establishment of FPAs. The results of this study indicate that S. barracuda has a greater response to protection than either C. fulva or C. cruentata. All species showed increasing total length trends going from unprotected to protected areas. Yet, neither species showed a significant difference in abundance between the two areas. This may be an indication that, at present, Bonaire’s FPAs are not effectively protecting S. barracuda, C. fulva, or C. cruentata.

This student research was retrieved from Physis: Journal of Marine Science X (Fall 2011)19: 28-34 from CIEE Bonaire.

Artificial reefs are commonly used to increase habitat space for reef-dwelling organisms. Coral reefs in Bonaire, Dutch Caribbean, are degrading due to factors such as disease, bleaching events, and heavy storms, reducing habitat space for reef fish. Two different artificial reefs were deployed on the leeward side of Bonaire in 2011: one block and one branching structure. Studies found that both reefs supported fish communities but utilization of the reefs by fish was not studied. The current study examines utilization of branching and block-style artificial reefs for foraging and feeding activities by herbivores and predators to assess which reef structure provides more resources for fish. Herbivore grazing and predator stalking rates were calculated as well as herbivory and predation pressure at increasing distances away from the artificial reef. The branching artificial reef supported more herbivore and predator activity compared to the block reef, suggesting structural complexity increases important sheltering and feeding areas for reef fish. Predation and herbivory pressures showed no trend with increasing distance from the artificial reef while predation pressure decreased with increasing distances from the natural reef. This suggests that the artificial reef may act as a shelter between the reef crest and the surrounding sand and rubble area, thereby increasing foraging distances of fish coming from the reef crest. Not only resident, but transient individuals, were found to use the artificial reefs for feeding and sheltering, suggesting that artificial reefs do not need to create permanent habitats in order to be important habitat for reef fish.

This student research was retrieved from Physis: Journal of Marine Science XI (Fall 2012)19: 46-57 from CIEE Bonaire.

Carbon dioxide levels in the ocean are predicted to double by the end of the century, making the marine environment more acidic than it is today. This study aimed to analyze whether increasing acidity affects antipredator survival behavior of the bridled goby, Coryphopterus glaucofraenum. A group of 10 adult gobies were treated with elevated CO2 levels, simulating predicted conditions by the year 2100, and another group of 10 were treated in present-day levels. Each group was exposed to the chemical cue of an injured conspecific, a predation chemical alarm signal, and the behavioral responses of each individual were recorded. The two groups were compared according to average time spent under shelter, number of feeding attempts, and amount of time spent motionless after exposure to cue. Overall, this experiment supported the hypothesis that gobies treated in acidified water would fail to fully exhibit such predator avoidance behaviors; gobies treated in elevated CO2 levels spent less time motionless after exposure to predation chemical cue. This study attempts to make important observations about the effect of environmental factors on fish behavior as well as far-reaching implications for the future survival of fish species and the stability of marine ecosystems as a whole.

This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 30-35 from CIEE Bonaire.

Understanding predator-prey relationships gives greater insight into coral reef health. A recent study on predator-prey relationships linked the relative brain mass of predators and their prey. Predation pressure forces prey to use decision making skills that require higher cognition by inspecting and identifying predators and then adjusting their behavior to achieve the highest chance for survival. However, the predation pressure that prey face outweighs the pressure predators face to find a prey. This results in prey having larger relative brain masses than their predators. There is little data on relative brain mass of fishes with few natural predators such as Pterois volitans. This study compared the brain mass to body mass ratio of P. volitans, which have very few natural predators and thus very little predation pressure, to the brain mass to body mass ratio of their prey, possible predators, competitors, and taxonomically similar fish. This study also analyzed the response of lionfish to divers with nets in order to investigate their ability to recognize divers as predators. Lionfish did swim away from divers 56.5% of the time which indicates that lionfish might be able to recognize divers as predators. Lionfish had a significantly smaller relative brain mass than their predators, prey, and competitors, but was not significantly smaller than taxonomically similar fish. These results demonstrate that the morphological antipredator adaptation of venomous spines cause very little predation pressure. Thus, lionfish are not forced to use the same cognitive skills as other prey or predators and in turn have smaller relative brain masses.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 10-20 from CIEE Bonaire.

Bonaire has long been considered to have amongst the healthiest reefs of the Caribbean. However, at the 2002 Annual Meeting of Pew Fellows for Marine Conservation in Bonaire, several scientists with a long history of research on Bonaire’s coral reefs, expressed concern over the future of the island’s reefs. Specifically, they identified the decline in large predatory fish such as groupers as a noticeable change during the past decade. They suspected that this change resulted from increased fishing pressure on Bonaire’s reefs. They also suggested the Bonaire authorities take action to protect the reef-fish stocks. In response to those concerns, officials of the Bonaire Marine Park consulted with scientists and fishermen on Bonaire to explore the possibility of establishing fish protected areas (FPAs), as a way to protect the reef fish stocks. If FPAs improve both fish stocks and the condition of the coral reef, all stakeholders will profit. If fish stocks increased significantly in FPAs, a “spill over” of these fish to adjacent fished areas would be expected. Also, fish that perform important ecological functions could improve the quality of the coral reef ecosystem. Therefore, areas protected from fishing should have healthier coral reefs, which would also improve the island’s valuable ecotourism businesses. The Pew Fellows program funded a research project designed to identify potential FPAs. The Bonaire Marine Park authority, in consultation with the local fishing community would determine the location and size of the FPAs. To monitor the effects of fish protection areas so fishing impacts can be isolated from other factors (such as natural changes, shore-based impacts or effects of scuba divers), an equal number of similar reef sites were selected for study, with half closed to fishing while half remaining open (as “control” reefs). This report reviews the status and recent trends of coral reefs in the Caribbean and Bonaire. It identifies the key features of healthy reefs and how Bonaire’s reefs compares with those elsewhere in the Caribbean. The seven chapters go into scientific detail on factors contributing to the condition of Bonaire’s reefs as of March and April 2003. Special focus will be on factors that threaten reef health or are critical to reef resilience such as seaweed overgrowth, nutrient inputs from land and the ecology of juvenile corals. The report concludes with chapters on the socioeconomic effects of Bonaire’s coral reefs on the fishing and diving industries that depend on them.
Summary Results 2003: The Biological Status of the Coral Reefs of Bonaire & Socioeconomic Implications
 In March and April of 2003, teams of researchers studied the coral reefs of Bonaire to establish the baseline conditions that currently exist and against which trends can be determined and future changes from fish protection areas be assessed. Six study sites were chosen with advice from the Bonaire Marine Park. They represent a range of comparable reefs minimally affected by the 1999 Hurricane Lenny. The sites selected for this study were: Windsock, Plaza, Forest on Klein Bonaire, Scientifico, Barcadera and Karpata (Fig. 0.4). When feasible, parallel studies were conducted at 5 and 10 m depths, however, only the latter depth had fully developed reefs at all sites. The study was designed to quantify the patterns of abundance of the dominant reef organisms as well as to study the processes that control their abundances or threaten their stability. This was done to establish a baseline and to determine if significant differences exist among any of the study sites that would make them a poor choice as a FPA. We also examined some socioeconomic factors related to fishing and scuba diving activities if FPAs are established in Bonaire.

Bonaire’s coral reefs remain among the healthiest in the Caribbean. Although the island’s reefs have suffered bleaching disturbances similar to those plaguing reefs throughout the Caribbean, they uniquely show signs of recovery. Here we highlight key findings from our March 2015 biennial coral reef monitoring expedition. We put the findings in the context of both the trends recorded since 2003 when we began our regular monitoring and the most recent research related to the factors controlling the structure and functioning of healthy coral reef ecosystems.