The Experts below are selected from a list of 77460 Experts worldwide ranked by ideXlab platform
Ray Hilborn - One of the best experts on this subject based on the ideXlab platform.
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evaluating impacts of forage Fish Abundance on marine predators
Conservation Biology, 2021Co-Authors: Christopher M Free, Olaf P Jensen, Ray HilbornAbstract:Forage Fish-small, low trophic level, pelagic Fish such as herrings, sardines, and anchovies-are important prey species in marine ecosystems and also support large commercial Fisheries. In many parts of the world, forage Fish Fisheries are managed using precautionary principles that target catch limits below the maximum sustainable yield. However, there are increasing calls to further limit forage Fish catch to safeguard their Fish, seabird, and marine mammal predators. The effectiveness of these extra-precautionary regulations, which assume that increasing prey Abundance increases predator productivity, are under debate. In this study, we used prey-linked population models to measure the influence of forage Fish Abundance on the population growth rates of 45 marine predator populations representing 32 Fish, seabird, and mammal species from 5 regions around the world. We used simulated data to confirm the ability of the statistical model to accurately detect prey influences under varying levels of influence strength and process variability. Our results indicate that predator productivity was rarely influenced by the Abundance of their forage Fish prey. Only 6 predator populations (13% of the total) were positively influenced by increasing prey Abundance and the model exhibited high power to detect prey influences when they existed. These results suggest that additional limitation of forage Fish harvest to levels well below sustainable yields would rarely result in detectable increases in marine predator populations.
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when does Fishing forage species affect their predators
Fisheries Research, 2017Co-Authors: Ray Hilborn, Olaf P Jensen, Ricardo O Amoroso, Eugenia Bogazzi, Ana M Parma, Cody S Szuwalski, Carl J WaltersAbstract:Abstract This paper explores the impact of Fishing low trophic level “forage” species on higher trophic level marine predators including other Fish, birds and marine mammals. We show that existing analyses using trophic models have generally ignored a number of important factors including (1) the high level of natural variability of forage Fish, (2) the weak relationship between forage Fish spawning stock size and recruitment and the role of environmental productivity regimes, (3) the size distribution of forage Fish, their predators and subsequent size selective predation (4) the changes in spatial distribution of the forage Fish as it influences the reproductive success of predators. We show that taking account of these factors generally tends to make the impact of Fishing forage Fish on their predators less than estimated from trophic models. We also explore the empirical relationship between forage Fish Abundance and predator Abundance for a range of U.S. Fisheries and show that there is little evidence for a strong connection between forage Fish Abundance and the rate of change in the Abundance of their predators. We suggest that any evaluation of harvest policies for forage Fish needs to include these issues, and that models tailored for individual species and ecosystems are needed to guide Fisheries management policy.
Olaf P Jensen - One of the best experts on this subject based on the ideXlab platform.
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evaluating impacts of forage Fish Abundance on marine predators
Conservation Biology, 2021Co-Authors: Christopher M Free, Olaf P Jensen, Ray HilbornAbstract:Forage Fish-small, low trophic level, pelagic Fish such as herrings, sardines, and anchovies-are important prey species in marine ecosystems and also support large commercial Fisheries. In many parts of the world, forage Fish Fisheries are managed using precautionary principles that target catch limits below the maximum sustainable yield. However, there are increasing calls to further limit forage Fish catch to safeguard their Fish, seabird, and marine mammal predators. The effectiveness of these extra-precautionary regulations, which assume that increasing prey Abundance increases predator productivity, are under debate. In this study, we used prey-linked population models to measure the influence of forage Fish Abundance on the population growth rates of 45 marine predator populations representing 32 Fish, seabird, and mammal species from 5 regions around the world. We used simulated data to confirm the ability of the statistical model to accurately detect prey influences under varying levels of influence strength and process variability. Our results indicate that predator productivity was rarely influenced by the Abundance of their forage Fish prey. Only 6 predator populations (13% of the total) were positively influenced by increasing prey Abundance and the model exhibited high power to detect prey influences when they existed. These results suggest that additional limitation of forage Fish harvest to levels well below sustainable yields would rarely result in detectable increases in marine predator populations.
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when does Fishing forage species affect their predators
Fisheries Research, 2017Co-Authors: Ray Hilborn, Olaf P Jensen, Ricardo O Amoroso, Eugenia Bogazzi, Ana M Parma, Cody S Szuwalski, Carl J WaltersAbstract:Abstract This paper explores the impact of Fishing low trophic level “forage” species on higher trophic level marine predators including other Fish, birds and marine mammals. We show that existing analyses using trophic models have generally ignored a number of important factors including (1) the high level of natural variability of forage Fish, (2) the weak relationship between forage Fish spawning stock size and recruitment and the role of environmental productivity regimes, (3) the size distribution of forage Fish, their predators and subsequent size selective predation (4) the changes in spatial distribution of the forage Fish as it influences the reproductive success of predators. We show that taking account of these factors generally tends to make the impact of Fishing forage Fish on their predators less than estimated from trophic models. We also explore the empirical relationship between forage Fish Abundance and predator Abundance for a range of U.S. Fisheries and show that there is little evidence for a strong connection between forage Fish Abundance and the rate of change in the Abundance of their predators. We suggest that any evaluation of harvest policies for forage Fish needs to include these issues, and that models tailored for individual species and ecosystems are needed to guide Fisheries management policy.
Christopher M Free - One of the best experts on this subject based on the ideXlab platform.
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evaluating impacts of forage Fish Abundance on marine predators
Conservation Biology, 2021Co-Authors: Christopher M Free, Olaf P Jensen, Ray HilbornAbstract:Forage Fish-small, low trophic level, pelagic Fish such as herrings, sardines, and anchovies-are important prey species in marine ecosystems and also support large commercial Fisheries. In many parts of the world, forage Fish Fisheries are managed using precautionary principles that target catch limits below the maximum sustainable yield. However, there are increasing calls to further limit forage Fish catch to safeguard their Fish, seabird, and marine mammal predators. The effectiveness of these extra-precautionary regulations, which assume that increasing prey Abundance increases predator productivity, are under debate. In this study, we used prey-linked population models to measure the influence of forage Fish Abundance on the population growth rates of 45 marine predator populations representing 32 Fish, seabird, and mammal species from 5 regions around the world. We used simulated data to confirm the ability of the statistical model to accurately detect prey influences under varying levels of influence strength and process variability. Our results indicate that predator productivity was rarely influenced by the Abundance of their forage Fish prey. Only 6 predator populations (13% of the total) were positively influenced by increasing prey Abundance and the model exhibited high power to detect prey influences when they existed. These results suggest that additional limitation of forage Fish harvest to levels well below sustainable yields would rarely result in detectable increases in marine predator populations.
Michelle J Paddack - One of the best experts on this subject based on the ideXlab platform.
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recent region wide declines in caribbean reef Fish Abundance
Current Biology, 2009Co-Authors: John D. Reynolds, Michelle J Paddack, Consuelo Aguilar, Richard S Appeldoorn, James P Beets, Edward W Burkett, Paul M Chittaro, Kristen Clarke, Rene EstevesAbstract:Profound ecological changes are occurring on coral reefs throughout the tropics [1-3], with marked coral cover losses and concomitant algal increases, particularly in the Caribbean region [4]. Historical declines in the Abundance of large Caribbean reef Fishes likely reflect centuries of overexploitation [5-7]. However, effects of drastic recent degradation of reef habitats on reef Fish assemblages have yet to be established. By using meta-analysis, we analyzed time series of reef Fish density obtained from 48 studies that include 318 reefs across the Caribbean and span the time period 1955-2007. Our analyses show that overall reef Fish density has been declining significantly for more than a decade, at rates that are consistent across all subregions of the Caribbean basin (2.7% to 6.0% loss per year) and in three of six trophic groups. Changes in Fish density over the past half-century are modest relative to concurrent changes in benthic cover on Caribbean reefs. However, the recent significant decline in overall Fish Abundance and its consistency across several trophic groups and among both Fished and nonFished species indicate that Caribbean Fishes have begun to respond negatively to habitat degradation.
Martin R Speight - One of the best experts on this subject based on the ideXlab platform.
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effects of habitat complexity on caribbean marine Fish assemblages
Marine Ecology Progress Series, 2005Co-Authors: Brian Gratwicke, Martin R SpeightAbstract:Sets of artificial reefs were replicated in 5 bays off Tortola in the British Virgin Islands to investigate the effects of habitat complexity on Fish assemblages. Increasing percentage hard sub- strate and the number of small reef holes increased Fish Abundance on reefs. The observed number of species (Sobs) occurring on each reef increased with increasing rugosity, variety of growth forms, percentage hard substrate, and variety of refuge hole sizes. A rarefied or Abundance-corrected spe- cies richness measure (Srare) was calculated to take the varying Fish Abundances into account. After this correction, rugosity was the only variable that significantly increased Fish species-richness. Experimental reefs of different height (20 and 60 cm) did not have significantly different Fish abun- dance or species richness. The presence of long-spined sea urchins Diadema antillarum increased Sobs and total Fish Abundance on artificial rock-reefs and in seagrass beds, but the effect was most pronounced in seagrass beds where shelter was a strongly limiting factor. These results indicate that complex habitats or animals such as D. antillarum that provide shelter to Fish are essential for main- taining Fish biodiversity at local scales. The most important aspects of complexity are rugosity, hard substrate and small refuge holes. Artificial reefs may be used to mitigate habitat damage in impacted areas, and if management objectives are to increase local Fish Abundance and species richness, the reefs should provide a stable substrate where this is unavailable, have a rugose surface with many small refuge holes, and have a variety of growth forms.
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the relationship between Fish species richness Abundance and habitat complexity in a range of shallow tropical marine habitats
Journal of Fish Biology, 2005Co-Authors: Brian Gratwicke, Martin R SpeightAbstract:A simple habitat assessment score (HAS) was designed to assess habitat complexity across several different shallow tropical marine habitats including sandy patches, algal beds, seagrass beds and reefs. It measured rugosity, variety of growth forms, height, refuge size categories, percentage live cover and percentage hard substratum. Multiple regression models using HAS variables as predictors accounted for 71 and 22% of the variation in observed species richness and total Fish Abundance respectively. The two most important predictors of observed species richness were rugosity and variety of growth forms, while height was the most important predictor of total Fish Abundance. The HAS method worked consistently across a variety of habitat types and the complexity map closely mirrored the map of observed species richness, reflecting the patchy habitat mosaic of shallow tropical marine areas. Stations at the mouth of an enclosed lagoon, however, had a higher number of species than might have been expected judging from the habitat complexity scores. It is possible that this was linked to the preferential settling of pelagic Fish larvae in this area as tidal water exchanges between the bay and the reef were funnelled through one small gap. This study highlights the need for Fish biodiversity studies to take habitat complexity into account.