Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller siz...Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller size-at-age, an earlier age-at-maturation and among others. Currently, the causes of these life history traits changes still require systematic analyses and empirical studies. The explanations that have been cited are merely expressed in terms of fish phenotypic adaptation. It has been claimed that the original traits of fish can be recovered once the intensity of exploitation of the fish is controlled. Sustained environmental and fishing pressure will change the life history traits of most fish species, so the fish individual's traits are still in small size-at-age and at earlier age-at-maturation in exploited fish populations. In this paper, we expressed our view of points that fishing gear has imposed selectivity on fish populations and individuals as various other environmental factors have done and such changes are unrecoverable. According to the existing tend of exploited fish individual's life history traits, we suggested further researches in this field and provided better methods of fishery management and thereby fishery resources protection than those available early.展开更多
Background With the widespread promotion of selective fishing which may target top predatory fishes,the abundance and species composition of top predators could change,which may further impact species at lower trophic...Background With the widespread promotion of selective fishing which may target top predatory fishes,the abundance and species composition of top predators could change,which may further impact species at lower trophic levels through a chain of cascading trophic interactions.However,the top-down effects of changes in predator communities driven by selective fishing remain poorly investigated.Methods Focusing on a seagrass ecosystem,we investigated how changes in two coexisting top predators(Lateolabrax japonicus and Acanthogobius ommaturus)under different selective fishing scenarios would affect species at lower trophic levels in a field manipulative experiment.Results We found that the trophic niches of A.ommaturus and L.japonicus overlapped greatly,although not completely.If loss of L.japonicus led to increases in A.ommaturus,the abundances of herbivorous benthos Barleeia bureri increased likely owing to A.ommaturus's suppression of low-level predators,while epiphyte and seagrass biomass decreased significantly likely owing to A.ommaturus's disturbance of seagrasses and sediments.If both predators were depleted,the biomasses of herbivorous benthos Cyclina sinensis and B.bureri increased significantly likely owing to the absence of top predators'disturbance of sediments,while epiphyte and seagrass biomass did not change.Conclusions Our study showed that loss of one top predator could lead to rapid changes in species at lower trophic levels in seagrass beds,depending on changes in,and the trophic or non-trophic effects(including biological disturbances)of,its competitors.Therefore,in fisheries resource management,the ecological impacts of selectively fishing a target predator must be managed considering changes in,and the trophic or non-trophic effects of,its competitors where present.展开更多
基金the financial support from Special Fund for Agro-scientific Research in the Public Interest (No. 201203018)
文摘Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller size-at-age, an earlier age-at-maturation and among others. Currently, the causes of these life history traits changes still require systematic analyses and empirical studies. The explanations that have been cited are merely expressed in terms of fish phenotypic adaptation. It has been claimed that the original traits of fish can be recovered once the intensity of exploitation of the fish is controlled. Sustained environmental and fishing pressure will change the life history traits of most fish species, so the fish individual's traits are still in small size-at-age and at earlier age-at-maturation in exploited fish populations. In this paper, we expressed our view of points that fishing gear has imposed selectivity on fish populations and individuals as various other environmental factors have done and such changes are unrecoverable. According to the existing tend of exploited fish individual's life history traits, we suggested further researches in this field and provided better methods of fishery management and thereby fishery resources protection than those available early.
基金funded by National Natural Science Foundation of China(Grant number 32425037,32271601)National Key Basic Research and Development Program(Grant number 2022YFC3105402)
文摘Background With the widespread promotion of selective fishing which may target top predatory fishes,the abundance and species composition of top predators could change,which may further impact species at lower trophic levels through a chain of cascading trophic interactions.However,the top-down effects of changes in predator communities driven by selective fishing remain poorly investigated.Methods Focusing on a seagrass ecosystem,we investigated how changes in two coexisting top predators(Lateolabrax japonicus and Acanthogobius ommaturus)under different selective fishing scenarios would affect species at lower trophic levels in a field manipulative experiment.Results We found that the trophic niches of A.ommaturus and L.japonicus overlapped greatly,although not completely.If loss of L.japonicus led to increases in A.ommaturus,the abundances of herbivorous benthos Barleeia bureri increased likely owing to A.ommaturus's suppression of low-level predators,while epiphyte and seagrass biomass decreased significantly likely owing to A.ommaturus's disturbance of seagrasses and sediments.If both predators were depleted,the biomasses of herbivorous benthos Cyclina sinensis and B.bureri increased significantly likely owing to the absence of top predators'disturbance of sediments,while epiphyte and seagrass biomass did not change.Conclusions Our study showed that loss of one top predator could lead to rapid changes in species at lower trophic levels in seagrass beds,depending on changes in,and the trophic or non-trophic effects(including biological disturbances)of,its competitors.Therefore,in fisheries resource management,the ecological impacts of selectively fishing a target predator must be managed considering changes in,and the trophic or non-trophic effects of,its competitors where present.
