Time filter

Source Type

Grand Cayman, Cayman Islands

Hawkes L.A.,Bangor University | Hawkes L.A.,University of Exeter | Tomas J.,University of Valencia | Tomas J.,University of Exeter | And 8 more authors.
Marine Ecology Progress Series | Year: 2012

The advent of telemetry has improved knowledge of the spatio-temporal distribution of marine species of conservation concern. Among the sea turtles, the movements of the hawksbill turtle Eretmochelys imbricata are among the least well described. We tracked 10 adult female hawksbill turtles by satellite after nesting in the Dominican Republic (DR) and describe a dichotomy in patterns of movement: some (n = 2) turtles remained in the DR, while others migrated to waters off Honduras and Nicaragua (n = 5) and the Bahamas (n = 1). Transmitters on 2 turtles failed during migration, before they reached their final foraging grounds. We present results from long tracking durations for 3 turtles, including 3 entire remigration intervals, high-lighting foraging ground and nest-site fidelity. Threats to hawksbill turtles are not well documented for Nicaragua or neighbouring Honduras and represent a major information gap. We suggest that directing conservation efforts to regionally important foraging areas, such as those in Nicaragua, and strengthening national conservation in each nation with significant hawksbill nesting offers a clear way forward for the conservation of hawksbill turtles in the region. © Inter-Research 2012 · www.int-res.com.

Camp E.F.,Central Caribbean Marine Institute | Lohr K.E.,Central Caribbean Marine Institute | Barry S.C.,Central Caribbean Marine Institute | Barry S.C.,University of Florida | And 4 more authors.
Bulletin of Marine Science | Year: 2013

Populations of the economically and ecologically important Nassau grouper, Epinephelus striatus Bloch, 1792, have declined to the point of being declared "endangered" by the International Union for the Conservation of Nature. Beyond existing efforts to reduce top-down pressure from overfishing, especially on spawning aggregations, recovery of Nassau grouper could be enhanced by preventing bottom-up pressures created by degradation of essential habitats. The design of suitable protection would benefit from knowledge of ontogenetic patterns in habitat use at multiple spatial scales, and this study documented microhabitat associations for late juvenile Nassau grouper in shallow, nearshore lagoons off Little Cayman Island. In total, 82% of juvenile grouper that were 12-26 cm in total length and approximately 1 yr old associated with hardbottom rather than other equally or more widespread microhabitats, i.e., sand, seagrass, and algae. Hardbottom provided crevices, holes, ledges, and other shelters. Approximately 96% of shelters contained a single juvenile grouper, and 10%-66% of these shelters also contained one or more cleaning organisms. These results suggest that protection of hardbottom in Little Cayman Island's lagoons would maintain the >1200 patches of microhabitat suitable for late juvenile Nassau grouper. © 2013 Rosenstiel School of Marine & Atmospheric Science of the University of Miami.

Archer S.K.,North Carolina State University | Archer S.K.,Florida International University | Allgeier J.E.,North Carolina State University | Allgeier J.E.,University of Georgia | And 9 more authors.
Coral Reefs | Year: 2015

Biogeochemical hot moments occur when a temporary increase in availability of one or more limiting reactants results in elevated rates of biogeochemical reactions. Many marine fish form transient spawning aggregations, temporarily increasing their local abundance and thus nutrients supplied via excretion at the aggregation site. In this way, nutrients released by aggregating fish could create a biogeochemical hot moment. Using a combination of empirical and modeling approaches, we estimate nitrogen and phosphorus supplied by aggregating Nassau grouper (Epinephelus striatus). Data suggest aggregating grouper supply up to an order-of-magnitude more nitrogen and phosphorus than daily consumer-derived nutrient supply on coral reefs without aggregating fish. Comparing current and historic aggregation-level excretion estimates shows that overfishing reduced nutrients supplied by aggregating fish by up to 87 %. Our study illustrates a previously unrecognized ecosystem viewpoint regarding fish spawning aggregations and provides an additional perspective on the repercussions of their overexploitation. © 2014, Springer-Verlag Berlin Heidelberg.

Heppell S.A.,Oregon State University | Semmens B.X.,University of California at San Diego | Archer S.K.,Oregon State University | Pattengill-Semmens C.V.,Reef Environmental Education Foundation REEF | And 4 more authors.
Biological Conservation | Year: 2012

Many spawning aggregations of marine fishes have been fished beyond the point of sustainability, leading to increased calls for protection through seasonal and/or site-specific fishery closures. Once a closure has been put in place, monitoring the aggregation is imperative in order to learn whether protection leads to the recovery of the population. Current methods for monitoring the status of spawning aggregations rely largely on counts, either subsample or census, usually combined with capturing a subset of the fish to assess individual traits such as length and weight. Handling fish during the spawning aggregation can be stressful for the fish, and can ultimately lead to decreased spawning success, increased susceptibility to predators, or increased mortality through capture trauma or infection. Here we present a novel analysis for monitoring fish on a spawning aggregation that does not require the capture and handling of fish. Following a recovering aggregation of Nassau grouper (. Epinephelus striatus) over seven spawning seasons, we show that length-distribution data can be collected by divers using a video-based system with parallel lasers calibrated to a specific distance apart, and subsequently use those data to monitor changes in the size distribution over time. We detected recruitment of new fish to the grouper spawning aggregation in the fourth year of monitoring. In addition to tracking size distribution trends over time, the length distribution information could be combined with an established length-weight regression and an estimate of total abundance to estimate spawning stock biomass. We qualitatively cross-validate this method with census data to evaluate its effectiveness in monitoring the recovery or decline of aggregating species that can be visually observed. © 2012 Elsevier Ltd.

Archer S.K.,Oregon State University | Heppell S.A.,Oregon State University | Semmens B.X.,Reef Environmental Education Foundation REEF | Pattengill-Semmens C.V.,Reef Environmental Education Foundation REEF | And 3 more authors.
Current Zoology | Year: 2012

Nassau grouper Epinephelus striatus are a large bodied, top level predator that is ecologically important throughout the Caribbean. Although typically solitary, Nassau grouper form large annual spawning aggregations at predictable times in specific locations. In 2003, The Cayman Islands Marine Conservation Board established protection for a newly rediscovered Nassau grouper spawning aggregation on Little Cayman, British West Indies. The large size of this aggregation provides a unique opportunity to study the behavior of Nassau grouper on a relatively intact spawning aggregation. During non-spawning periods Nassau grouper display a reddish-brown-and-white barred coloration. However, while aggregating they exhibit three additional color phases: "bicolor", "dark", and "white belly". We video sampled the population on multiple days leading up to spawning across five spawning years. Divers focused a laser caliper equipped video camera on individual fish at the aggregation. We later analyzed the video to determine the length of the fish and record the color phase. Our observations show that the relative proportion of fish in the bicolor color phase increases significantly on the day leading up to the primary night of spawning. The increase in the proportion of the bicolor color phase from 0.05 early in the aggregation to 0.40 on the day of spawning suggests that this color phase conveys that a fish is behaviorally and physiologically prepared to spawn. Additionally, 82.7% of fish exhibiting dark or white belly coloration early in the aggregation period suggests that these color phases are not only shown by female fish as was previously posited. ©2012 Current Zoology.

Discover hidden collaborations