This paper presents results from a study conducted as part of REEF's Grouper Moon Project, evaluating the potential ecosystem-level effect of Nassau Grouper aggregations. In particular, the study looked at the impact the spawning aggregation has in creating biogeochemical "hot moments", which occur when a temporary increase in availability of one or more limiting nutrients results in elevated rates of biogeochemical reactions. In this case, the limited nutrients are nitrogen and phosphorus, and the temporary increase is resulting from all of the grouper excrement that results when approximately 5,000 Nassau Grouper gather in a small area for 10 days during the spawning season.
Information on fish movement and growth is primarily obtained through the marking and tracking of individuals with external tags, which are usually affixed to anesthetized individuals at the surface. However, the quantity and quality of data obtained by this method is often limited by small sample sizes owing to the time associated with the tagging process, high rates of tagging-related mortality, and displacement of tagged individuals from the initial capture location. To address these issues, we describe a technique for applying external streamer and dart tags in situ, which uses SCUBA divers to capture and tag individual fish on the sea floor without the use of anesthetic. We demonstrate this method for Indo-Pacific lionfish (Pterois volitans/P. miles), species which are particularly vulnerable to barotrauma when transported to and handled at the surface. To test our method, we tagged 161 individuals inhabiting 26 coral reef locations in the Bahamas over a period of 3 years. Our method resulted in no instances of barotrauma, reduced handling and recovery time, and minimal post-tagging release displacement compared with conventional ex situ tag application. Opportunistic resighting and recapture of tagged individuals reveals that lionfish exhibit highly variable site fidelity, movement patterns, and growth rates on invaded coral reef habitats. In total, 24% of lionfish were resighted between 29 and 188 days after tagging. Of these, 90% were located at the site of capture, while the remaining individuals were resighted between 200 m and 1.1 km from initial site of capture over 29 days later. In situ growth rates ranged between 0.1 and 0.6 mm/day. While individuals tagged with streamer tags posted slower growth rates with increasing size, as expected, there was no relationship between growth rate and fish size for individuals marked with dart tags, potentially because of large effects of tag presence on the activities of small bodied lionfish (i.e., <150 mm), where the tag was up to 7.6% of the lionfish's mass. Our study offers a novel in situ tagging technique that can be used to provide critical information on fish site fidelity, movement patterns, and growth in cases where ex situ tagging is not feasible.
The study, conducted by Dr. Stephanie Green (OSU/REEF), Lad Akins (REEF), and others, confirms for the first time that controlling lionfish populations in the western Atlantic Ocean can pave the way for a recovery of native fish. Even if it's one speared fish at a time, data are showing that removals can be effective. And not every lionfish need be removed…the research findings document that reducing lionfish numbers by specified amounts will allow a rapid recovery of native fish biomass. Over 18 months, the biomass of native prey fishes increased an average 50-70% on reefs where lionfish numbers were suppressed below target levels predicted to cause prey depletion. On reefs where lionfish numbers remained higher than target levels, the biomass of prey fishes decreased by a further 50%. While complete eradication of lionfish from the Caribbean is not likely, groups are actively removing them from coastal areas (mostly via spear and net). This study is a first step in showing that strategic local efforts that suppress the invasion to low levels can help protect and recover native fish communities affected by lionfish. This ground-breaking invasive lionfish research was conducted as a collaboration between REEF, Oregon State University, Simon Fraser University, and the Cape Eleuthera Institute.
This study, co-authored by scientists from REEF's Grouper Moon Project, evaluated genetic connectedness between Nassau Grouper populations throughout the Caribbean. The authors obtained genetic tissue samples from 620 Nassau Grouper from 19 sites across 9 countries, including the Cayman Islands. They found evidence for strong genetic differentiation among Nassau Grouper subpopulations throughout the Caribbean. These results suggest that, despite a lack of physical barriers, Nassau grouper form multiple distinct subpopulations in the Caribbean Sea. Oceanography (regional currents, eddies) likely plays an important role in retaining larvae close to spawning sites at both local and regional spatial scales. These findings highlight the importance of conservation initiatives such at REEF's Grouper Moon program in the Cayman Islands.
Frequent culling of the invasive Indo-Pacific Lionfish throughout the Caribbean has been shown to cause a shift towards more wary and reclusive behaviour by lionfish, which has prompted calls for halting culls. This paper, co-authored by REEF Lionfish Program researchers, addresses those concerns and reviews research conducted by REEF and other research efforts. Culling successfully lowers lionfish numbers and has been shown to stabilise or even reverse declines in native prey fish. Partial culling is often as effective as complete local eradication, yet requires significantly less time and effort. Abandoning culling altogether would therefore be seriously misguided and a hindrance to conservation. The authors also offer suggestions for how to design removal programs that minimize behavioural changes and maximize culling success.
The authors of this study (including REEF staff Lad Akins) examined the recent case of Indo-Pacific lionfish invading Northern Gulf of Mexico coastal waters. The authors compared traditional reef fish monitoring efforts to less traditional data including the observations of divers through REEF's Volunteer Fish Survey Project and spearfishers. They found that citizen observations documented lionfish 1-2 years earlier and more frequently than the more traditional monitoring efforts. The authors also explored the willingness of spearfishers to help minimize impacts of the invasion by harvesting lionfish. They found that spearfishers who had encountered more lionfish while diving perceived them as more harmful to the habitat than less experienced divers and were also more likely to participate in harvesting initiatives. The authors also report that encouragement from scientists and managers was a far better motivator than the desire to harvest lionfish for personal consumption. This study demonstrates the value of engaging citizens for assessing and responding to large-scale and time-sensitive conservation problems.
There is an increasing need to examine regional patterns of diversity in coral-reef systems because their biodiversity is declining globally. The authors used REEF data from 80 sites from 6 eco-regions throughout the Caribbean to evaluate patterns of biodiversity. Specifically, they used "additive partitioning", which quantifies the contribution of different types of diversity (alpha and beta; comparing diversity between sites within a region and between regions) to total diversity across different spatial scales. The primary objective was to identify patterns of reef-fish diversity across multiple spatial scales under different scenarios, examining factors such as fisheries and demographic connectivity. Total diversity at the Caribbean scale was attributed to β-diversity (nearly 62% of the species), with the highest β-diversity at the site scale. α⎯⎯-diversity was higher than expected by chance in all scenarios and at all studied scales.
This suggests that fish assemblages are more homogenous than expected, particularly at the ecoregion scale. Within each ecoregion, diversity was mainly attributed to alpha, except for the Southern ecoregion where there was a greater difference in species among sites. β-components were lower than expected in all ecoregions, indicating that fishes within each ecoregion are a subsample of the same species pool. The scenario involving the effects of fisheries showed a shift in dominance for β-diversity from regions to subregions, with no major changes to the diversity patterns. In contrast, demographic connectivity partially explained the diversity pattern. β-components were low within connectivity regions and higher than expected by chance when comparing between them. The author's results highlight the importance of ecoregions as a spatial scale to conserve local and regional coral reef-fish diversity.
The authors describe the behavioral interactions of piscivorous mid-water and demersal fishes at subtropical live-bottom reefs off the coast of Georgia and off the west coast of Florida in the northeast Gulf of Mexico. The observations are used to construct a topological behavior web of the interactions of mid-water and demersal piscivores, their prey, and those associated species that modify predator-prey interactions. Results show that inter-specific behavioral interactions are common attributes of piscivores in these reef fish communities. The authors propose a framework for assessing the demographic consequences of such interactions. Data for this study were collected using a modified Roving Diver Technique, the method employed by REEF surveyors. One of the co-authors, Dave Grenda, is a member of REEF's Advanced Assessment Team.
Research conducted by Dr. Ben Holt from University of East Angila in the UK shows that methods to record marine diversity used by REEF surveyors returned results consistent with techniques favoured by peer-reviewed science. The findings give weight to the growing phenomenon of citizen science programs such as REEF's Volunteer Survey Project. The field study compared methods used by REEF volunteer SCUBA divers with those used by professional scientists to measure the variety of fish species in three Caribbean sites in the Turks and Caicos. The divers surveyed the sites using two methods – the 'belt transect', used in peer reviewed fish diversity studies, and the 'roving diver technique', used by REEF volunteers. Two teams of 12 divers made 144 separate underwater surveys across the sites over four weeks. While the traditional scientific survey revealed sightings of 106 different types of fish, the volunteer technique detected greater marine diversity with a total of 137 in the same waters. Dr Holt led the research in partnership with the Centre for Marine Resource Studies in the Caribbean and the University of Copenhagen, Denmark. He said: "The results of this study are important for the future of citizen science and the use of data collected by these programs. Allowing volunteers to use flexible and less standardised methods has important consequences for the long term success of citizen science programs. Amateur enthusiasts typically do not have the resources or training to use professional methodology. Our study demonstrates the quality of data collected using a volunteer method can match, and in some respects exceed, protocols used by professional scientists."
This paper presents reconstructions of coral reef food webs in three Greater Antillean regions of the Caribbean: the Cayman Islands, Cuba, and Jamaica. The REEF Volunteer Fish Survey Project dataset is one of several used to construct the food webs. The datasets presented in this publication will facilitate comparisons of historical and regional variation, the assessment of impacts of species loss and invasion, and the application of food webs to ecosystem analyses (e.g. Coral Reefs in Crisis: The Reliability of Deep-Time Food Web Reconstructions as Analogs for the Present, 2018, PD Roopnarine and AA Dineen)