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Injuries from non-retention in gillnet fisheries suppress reproductive maturation in escaped fish.

Baker MR, Swanson P, Young G - PLoS ONE (2013)

Bottom Line: We found evidence for elevated stress in fish injured via non-retention in gillnet fisheries.We also analyzed sex steroid concentrations in females (estradiol-17β and 17,20β-dihydroxy-4-pregnen-3-one) to determine whether non-retention impairs reproductive potential in escaped individuals.These findings have important implications for effective conservation and management of exploited fish stocks and suggest means to improve spawning success in such stocks if retention in commercial fisheries is improved and incidental mortality reduced.

View Article: PubMed Central - PubMed

Affiliation: School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, United States of America. Matthew.Baker@noaa.gov

ABSTRACT
Exploitation of fisheries resources has unintended consequences, not only in the bycatch and discard of non-target organisms, but also in damage to targeted fish that are injured by gear but not landed (non-retention). Delayed mortality due to non-retention represents lost reproductive potential in exploited stocks, while not contributing to harvest. Our study examined the physiological mechanisms by which delayed mortality occurs and the extent to which injuries related to disentanglement from commercial gear compromise reproductive success in spawning stocks of Pacific salmon (Oncorhynchus spp.). We found evidence for elevated stress in fish injured via non-retention in gillnet fisheries. Plasma cortisol levels correlated with the severity of disentanglement injury and were elevated in fish that developed infections related to disentanglement injuries. We also analyzed sex steroid concentrations in females (estradiol-17β and 17,20β-dihydroxy-4-pregnen-3-one) to determine whether non-retention impairs reproductive potential in escaped individuals. We demonstrate evidence for delayed or inhibited maturation in fish with disentanglement injuries. These findings have important implications for effective conservation and management of exploited fish stocks and suggest means to improve spawning success in such stocks if retention in commercial fisheries is improved and incidental mortality reduced.

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Related in: MedlinePlus

Top Panel: Sockeye salmon at in-river migration, (early-stage maturation, top left) and at spawning streams (late-stage maturation, top right).Middle Panel: Sockeye salmon categorized according to severity of non-retention injury as sampled at spawning streams. Traits associated with sexual maturity, such as darker coloration (both sexes), absorbed scales (both sexes), dorsal-ventral elongation (males), and increased kype length (males) are typically reduced as a function of increased severity of disentanglement injury. Bottom Panel: Propeller injuries were characterized by a clean cut with limited extent in contrast to gillnet disentanglement injuries, characterized by multiple points of contact with lacerations spanning the circumference of the fish (bottom left). Fungal infection, Saprolegnia spp. (bottom right).
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pone-0069615-g001: Top Panel: Sockeye salmon at in-river migration, (early-stage maturation, top left) and at spawning streams (late-stage maturation, top right).Middle Panel: Sockeye salmon categorized according to severity of non-retention injury as sampled at spawning streams. Traits associated with sexual maturity, such as darker coloration (both sexes), absorbed scales (both sexes), dorsal-ventral elongation (males), and increased kype length (males) are typically reduced as a function of increased severity of disentanglement injury. Bottom Panel: Propeller injuries were characterized by a clean cut with limited extent in contrast to gillnet disentanglement injuries, characterized by multiple points of contact with lacerations spanning the circumference of the fish (bottom left). Fungal infection, Saprolegnia spp. (bottom right).

Mentions: Non-retention (here defined as active or passive disentanglement from capture gear, rather than deliberate release by humans) is prevalent in commercial fisheries, but there is limited knowledge of the consequences to escaped fish and impacts of unaccounted mortality [1], [2]. Physiological analyses provide an opportunity to examine mechanisms [3], which cause escape mortality. Salmon (Oncorhynchus spp.) stocks in Alaska are managed to ensure sustainable production by allowing a fixed number of adult fish to escape commercial fisheries and return to natal sites to spawn [4], [5]. In stocks subject to harvest with commercial gillnets, many fish that ultimately escape may temporarily entangle in nets while migrating through fishing districts (Fig. 1). Non-retention in gillnet fisheries leads to disentanglement injuries in escaped fish and may degrade the reproductive potential of spawning stocks. Previous studies [6], [7] have demonstrated that such injuries have detrimental effects, delaying sexual maturation and timing of spawning, and often result in pre-spawning mortality. In this study we reveal the mechanisms by which delayed mortality and spawning failure might occur.


Injuries from non-retention in gillnet fisheries suppress reproductive maturation in escaped fish.

Baker MR, Swanson P, Young G - PLoS ONE (2013)

Top Panel: Sockeye salmon at in-river migration, (early-stage maturation, top left) and at spawning streams (late-stage maturation, top right).Middle Panel: Sockeye salmon categorized according to severity of non-retention injury as sampled at spawning streams. Traits associated with sexual maturity, such as darker coloration (both sexes), absorbed scales (both sexes), dorsal-ventral elongation (males), and increased kype length (males) are typically reduced as a function of increased severity of disentanglement injury. Bottom Panel: Propeller injuries were characterized by a clean cut with limited extent in contrast to gillnet disentanglement injuries, characterized by multiple points of contact with lacerations spanning the circumference of the fish (bottom left). Fungal infection, Saprolegnia spp. (bottom right).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3722223&req=5

pone-0069615-g001: Top Panel: Sockeye salmon at in-river migration, (early-stage maturation, top left) and at spawning streams (late-stage maturation, top right).Middle Panel: Sockeye salmon categorized according to severity of non-retention injury as sampled at spawning streams. Traits associated with sexual maturity, such as darker coloration (both sexes), absorbed scales (both sexes), dorsal-ventral elongation (males), and increased kype length (males) are typically reduced as a function of increased severity of disentanglement injury. Bottom Panel: Propeller injuries were characterized by a clean cut with limited extent in contrast to gillnet disentanglement injuries, characterized by multiple points of contact with lacerations spanning the circumference of the fish (bottom left). Fungal infection, Saprolegnia spp. (bottom right).
Mentions: Non-retention (here defined as active or passive disentanglement from capture gear, rather than deliberate release by humans) is prevalent in commercial fisheries, but there is limited knowledge of the consequences to escaped fish and impacts of unaccounted mortality [1], [2]. Physiological analyses provide an opportunity to examine mechanisms [3], which cause escape mortality. Salmon (Oncorhynchus spp.) stocks in Alaska are managed to ensure sustainable production by allowing a fixed number of adult fish to escape commercial fisheries and return to natal sites to spawn [4], [5]. In stocks subject to harvest with commercial gillnets, many fish that ultimately escape may temporarily entangle in nets while migrating through fishing districts (Fig. 1). Non-retention in gillnet fisheries leads to disentanglement injuries in escaped fish and may degrade the reproductive potential of spawning stocks. Previous studies [6], [7] have demonstrated that such injuries have detrimental effects, delaying sexual maturation and timing of spawning, and often result in pre-spawning mortality. In this study we reveal the mechanisms by which delayed mortality and spawning failure might occur.

Bottom Line: We found evidence for elevated stress in fish injured via non-retention in gillnet fisheries.We also analyzed sex steroid concentrations in females (estradiol-17β and 17,20β-dihydroxy-4-pregnen-3-one) to determine whether non-retention impairs reproductive potential in escaped individuals.These findings have important implications for effective conservation and management of exploited fish stocks and suggest means to improve spawning success in such stocks if retention in commercial fisheries is improved and incidental mortality reduced.

View Article: PubMed Central - PubMed

Affiliation: School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, United States of America. Matthew.Baker@noaa.gov

ABSTRACT
Exploitation of fisheries resources has unintended consequences, not only in the bycatch and discard of non-target organisms, but also in damage to targeted fish that are injured by gear but not landed (non-retention). Delayed mortality due to non-retention represents lost reproductive potential in exploited stocks, while not contributing to harvest. Our study examined the physiological mechanisms by which delayed mortality occurs and the extent to which injuries related to disentanglement from commercial gear compromise reproductive success in spawning stocks of Pacific salmon (Oncorhynchus spp.). We found evidence for elevated stress in fish injured via non-retention in gillnet fisheries. Plasma cortisol levels correlated with the severity of disentanglement injury and were elevated in fish that developed infections related to disentanglement injuries. We also analyzed sex steroid concentrations in females (estradiol-17β and 17,20β-dihydroxy-4-pregnen-3-one) to determine whether non-retention impairs reproductive potential in escaped individuals. We demonstrate evidence for delayed or inhibited maturation in fish with disentanglement injuries. These findings have important implications for effective conservation and management of exploited fish stocks and suggest means to improve spawning success in such stocks if retention in commercial fisheries is improved and incidental mortality reduced.

Show MeSH
Related in: MedlinePlus