Direct and indirect fishery effects on small coastal elasmobranchs in the northern Gulf of Mexico

Shepherd, Travis D.; Myers, Ransom A.

doi:10.1111/j.1461-0248.2005.00807.x

Cited by 150 publications

(146 citation statements)

References 33 publications

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“…Overall, biomass declined 89.7% and large predators declined by 90.3%-the same as the declines originally reported by Myers and Worm (4). Perhaps more important than the actual magnitude of decline, however, is the clear shift in species composition and relative abundance in the pelagic community reminiscent of the increase in mesopredators in the northwest Atlantic and Gulf of Mexico (30,33). Pelagic fisheries are a vast uncontrolled experiment whose ecosystem consequences are still unknown.…”

Section: The Open Ocean Pelagic Realmsupporting

confidence: 54%

“…Likewise, in the Gulf of Mexico, longline fishing and trawling reduced the four commonest large pelagic species by 45-99% in the 40 years between the 1950s and 1990s (32). Small coastal sharks in the Gulf of Mexico have also been severely reduced, except for some species that have experienced release from predation by the overfishing of their predators (33). Of the 23 species for which adequate data were available, 16 species declined between 1972 and 2002, and the declines were statistically significant for 9 species, 3 of which were reduced to Ͻ2% of their 1972 abundance.…”

Section: Continental Shelvesmentioning

confidence: 99%

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Ecological extinction and evolution in the brave new ocean

Jackson

2008

Proc. Natl. Acad. Sci. U.S.A.

460

312

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The great mass extinctions of the fossil record were a major creative force that provided entirely new kinds of opportunities for the subsequent explosive evolution and diversification of surviving clades. Today, the synergistic effects of human impacts are laying the groundwork for a comparably great Anthropocene mass extinction in the oceans with unknown ecological and evolutionary consequences. Synergistic effects of habitat destruction, overfishing, introduced species, warming, acidification, toxins, and massive runoff of nutrients are transforming once complex ecosystems like coral reefs and kelp forests into monotonous level bottoms, transforming clear and productive coastal seas into anoxic dead zones, and transforming complex food webs topped by big animals into simplified, microbially dominated ecosystems with boom and bust cycles of toxic dinoflagellate blooms, jellyfish, and disease. Rates of change are increasingly fast and nonlinear with sudden phase shifts to novel alternative community states. We can only guess at the kinds of organisms that will benefit from this mayhem that is radically altering the selective seascape far beyond the consequences of fishing or warming alone. The prospects are especially bleak for animals and plants compared with metabolically flexible microbes and algae. Halting and ultimately reversing these trends will require rapid and fundamental changes in fisheries, agricultural practice, and the emissions of greenhouse gases on a global scale.A bout 10 years ago, several of us concluded that the global ecological condition of the oceans because of overfishing was as dire as that of tropical rain forests, and that future losses would be enormous and potentially irreversible if action were not taken promptly to reverse the trajectories of decline (1-4). The scientific response was chilly, as evidenced by the statement of task for the recent National Research Council (NRC) report on the dynamics of marine ecosystems (5), which refers to our work in terms that emphasize the ''high profile'' of the articles (as if this were unseemly), the unconventional (and therefore suspect) nature of the data, and our assertions about the importance of shifting baselines and fishing down marine food webs, and that 90% of large predatory fish stocks are gone. In the end, the NRC report cautiously confirmed the conclusions it was convened to evaluate. But many scientists remain skeptical, apparently because (i) most conclusions are necessarily based on patterns and correlations using data gathered for many different purposes rather than experiments, (ii) the traditional emphasis in biological oceanography on bottom-up nutrient forcing rather than top-down control by predators, and (iii) the strong implication that most fisheries have been mismanaged for decades.The focus of the NRC report (5) was on fishing, but the problems are vastly greater because of the additional effects on marine ecosystems of biological, toxic, and nutrient pollution, habitat loss, global climate change, and the synerg...

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Section: The Open Ocean Pelagic Realmsupporting

confidence: 54%

Section: Continental Shelvesmentioning

confidence: 99%

Ecological extinction and evolution in the brave new ocean

Jackson

2008

Proc. Natl. Acad. Sci. U.S.A.

460

312

View full text Add to dashboard Cite

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“…A growing body of literature has reported a strong relationship between fishing and decreases in abundance of populations of top predators, with depletions reported to reach such critical levels as 90% of virgin. These reductions have been documented in coastal, benthic, demersal, and pelagic environments and are associated with different fisheries (Baum et al, 2003;Ferretti et al, 2008;Shepherd & Myers, 2005). The decrease in top predator abundance has allegedly led to community restructuring, with their composition (richness and abundance) now being dominated by medium-sized species with lower trophic levels Lotze et al, 2011;Myers et al, 2007).…”

Section: Effects Of Fishing On the Function Of Trophic Networkmentioning

confidence: 99%

Changes to Marine Trophic Networks Caused by Fishing

Navia¹,

Cortés²,

Jordán³

et al. 2012

Diversity of Ecosystems

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“…Stevens et al 2000a, Myers & Worm 2003, Bascompte et al 2005, Shepherd & Myers 2005, Myers et al 2007. Their capacity to influence community composition and relative abundance of prey species likely provides trophic stability over some time scales, and this capacity is in itself affected by habitat use, movement and distribution patterns.…”

Section: Introductionmentioning

confidence: 99%

Complexities of coastal shark movements and their implications for management

Speed

Field²,

Meekan

et al. 2010

Mar. Ecol. Prog. Ser.

268

239

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Global declines of shark populations are of concern because of their largely assumed role as moderators of ecosystem function. Without long-term data on movement patterns for many species, it is impossible to infer relative extinction risk, which varies as a function of range, dispersal and habitat specificity and use. The past 50 yr of research on coastal sharks has revealed common movement patterns among species. In the horizontal plane, measured home range size generally increases with body size. We demonstrate meta-analytically the effects of increasing body size and monitoring time on home range size. Changes in the extent of horizontal movement might arise from ontogeny, predator avoidance or environmental tolerances. In the vertical plane, movement patterns include oscillatory vertical displacement, surface swimming, diel vertical migration and swimming at depth. These vertical movements are often attributed to foraging or navigation, but have been quantified less than horizontal patterns. Habitat specificity is often correlated with environmental conditions such as depth, salinity, substratum, and in some cases, prey availability. Site fidelity is common in species that use nursery areas. However, fidelity to mating, pupping, feeding and natal sites has only been observed in a few species. To date, few studies have examined habitat partitioning, although some general patterns have emerged: habitats appear to be subdivided by benthos type, prey availability and depth. The conservation of coastal sharks can be facilitated in some cases by the use of marine protected areas, especially for coastal resident species using specific nursery, reproduction or feeding areas. Partial protected-area closures might be effective during aggregation or migration periods to protect older size classes, but these must be applied with other management strategies such as reduced fishing and size or bag limits to protect individuals throughout different life history phases. More long-term research on habitat use, migration patterns and habitat partitioning is essential for developing successful management initiatives for coastal shark populations.

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Direct and indirect fishery effects on small coastal elasmobranchs in the northern Gulf of Mexico

Cited by 150 publications

References 33 publications

Ecological extinction and evolution in the brave new ocean

Ecological extinction and evolution in the brave new ocean

Changes to Marine Trophic Networks Caused by Fishing

Complexities of coastal shark movements and their implications for management

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