Global estimates of shark catches using trade records from commercial markets

Clarke, Shelley; McAllister, Murdoch K.; Milner‐Gulland, E. J.; Kirkwood, G.P.; Michielsens, Catherine; Agnew, David J.; Pikitch, Ellen K.; Nakano, Hirofumi; Shivji, Mahmood S.

doi:10.1111/j.1461-0248.2006.00968.x

Cited by 427 publications

(381 citation statements)

References 29 publications

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“…However, in recent decades they have been subject to very high mortality, especially as the high demand for shark fins made them a lucrative bycatch species in long-line fisheries (Clarke et al 2006). Thus, the silky shark population in the Gulf of Mexico has declined by more than 90% since the 1950s (Baum and Myers 2004), and it has been estimated that fishing mortality in the northwest Atlantic would need to be reduced by~60% to ensure the survival of this sensitive species (Myers and Worm 2005).…”

Section: Introductionmentioning

confidence: 99%

Reef-use and residency patterns of a baited population of silky sharks, Carcharhinus falciformis, in the Red Sea

Clarke¹,

Lea²,

Ormond³

2011

Mar. Freshwater Res.

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Many shark populations are experiencing critical declines from overfishing, triggering potentially detrimental cascade effects on marine ecosystems. Silky sharks, Carcharhinus falciformis, have experienced some of the most severe declines, yet little information exists on their behavioural ecology to inform management decisions. In the present study, the movement patterns of a sexually segregated subpopulation of female silky sharks on reefs in the Central Red Sea were investigated using acoustic telemetry to characterise habitat-use and residency patterns. Frequent baiting of sharks at a particular reef-site significantly increased time spent in the vicinity, although no increases in use of other reef areas 5–10 and 50–60 km away were recorded, and regular use of all three reef areas persisted in the absence of bait. Observed residency patterns varied considerably, from being present almost year-round to visiting only intermittently. The sharks spent significantly longer times at study reefs during daylight hours, even within bait-free regions, suggesting the diel bias is normal. This pattern became less distinct nearer the full moon when there is more ambient light. The regular, perennial use of these reefs by mature and near-mature female silky sharks highlights the importance of this habitat in the Red Sea for recruitment into the local shark population.

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Section: Introductionmentioning

confidence: 99%

Reef-use and residency patterns of a baited population of silky sharks, Carcharhinus falciformis, in the Red Sea

Clarke¹,

Lea²,

Ormond³

2011

Mar. Freshwater Res.

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“…Coupled with high rates of exploitation (6-8% yr -1 ) by fishing in response to market demand (Clarke et al 2006;Worm et al 2013), this has resulted in many populations of sharks being depleted at a rate that exceeds their natural recovery potential (Worm et al 2013). In tropical ecosystems, fishing has caused declines in common species of sharks in many localities worldwide.…”

Section: Introductionmentioning

confidence: 99%

Evidence for rapid recovery of shark populations within a coral reef marine protected area

Speed

Cappo

Meekan

2018

Biological Conservation

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There is limited evidence on the rate at which the shark populations of coral reefs can rebound from over-exploitation, the baselines that might signify when recovery has occurred and the role of no-take Marine Protected Areas (MPA) in aiding this process. We surveyed shark assemblages at Ashmore Reef in Western Australia using baited remote underwater video Stations in 2004 prior to enforcement of MPA status and then again in 2016 after eight years of strict enforcement. We found an increase in the relative mean abundance of Carcharhinus amblyrhynchos from 0.16 ± 0.06 individuals/hr -1 in 2004 to 0.74 ± 0.11 individuals/hr -1 in 2016, a change that was also accompanied by a shift in the assemblage of sharks to greater proportions of apex species (from 7.1% to 11.9%) and reef sharks (from 28.6% to 57.6%), and a decrease in the proportional abundance of lower trophic level species (from 64.3% to 30.5%). Abundances and trophic assemblage of sharks at Ashmore Reef in 2004 resembled those of the Scott Reefs, where targeted fishing for sharks still occurs, whereas in 2016, abundances and trophic structures had recovered to resemble those of the Rowley Shoals, a reef system that has been a strictly enforced MPA for over 25 years. The shift in abundance and community structure coincident with strict enforcement of the MPA at Ashmore Reef has occurred at a rate greater than predicted by demographic models, implying the action of compensatory processes in recovery. Our study shows that shark communities can recover rapidly after exploitation in a well-managed no-take MPA.

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“…'Taxonomic resolution' describes the commonly reported taxonomic levels, which often correspond to the highest possible taxonomic resolution for each survey method. CPUE: catch per unit effortMar Ecol Prog Ser 566: [117][118][119][120][121][122][123][124][125][126][127][128][129][130][131][132][133][134] 2017 tion undermine these estimates of population status (Burgess et al 2005, Clarke et al 2006, Dulvy et al 2008. Written accounts, ship logbooks, and artifacts, although often qualitative or isolated in time and space, provide the only indication of shark abundance before this period (Holden 1977, Ferretti et al 2008, Drew et al 2013; Table 6).…”

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confidence: 99%

Dermal denticles as a tool to reconstruct shark communities

Dillon¹,

Norris²,

O’Dea³

2017

Mar. Ecol. Prog. Ser.

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The last 50 yr of fisheries catch statistics and ecological surveys have reported significant decreases in shark populations, which have largely been attributed to human activities. However, sharks are challenging to census, and this decline likely pre-dated even the longest fishery-dependent time series. Here we present the first use of dermal denticles preserved in reef sediments as a novel tool to reconstruct shark communities. We first built a dermal denticle reference collection and conducted a morphometric analysis of denticle characters to relate denticle form to taxonomy, shark ecology, and denticle function. Denticle morphology was highly variable across the body of an individual shark and between taxa, preventing species-or genus-level identification of isolated denticles. However, we found that denticle morphology was strongly correlated with shark ecology, and morphometric analysis corroborated existing functional classifications. In a proof of concept, we extracted 330 denticles from modern and fossil reef sediments in Bocas del Toro, Panama and found them to be morphologically diverse and sufficiently well-preserved to allow classification. We observed a high degree of correspondence between the denticles found in the sediments and the sharks documented in the region. We therefore propose that (1) denticle assemblages in the recent fossil record can help establish quantitative pre-human shark baselines and (2) time-averaged denticle assemblages on modern reefs can supplement traditional surveys, which may prove especially valuable in areas where rigorous surveys of sharks are difficult to perform.KEY WORDS: Dermal denticle · Functional morphology · Shark · Paleoecology · Baseline 566: 117-134, 2017 diurnal and seasonal movement patterns prevent sharks from being meaningfully censused in many regions (Sale & Douglas 1981, MacNeil et al. 2008, Ward-Paige et al. 2010a, McCauley, et al. 2012a. Time series or replicated surveys have also shown conflicting trends for the same area depending on the survey method used and its associated biases (Burgess et al. 2005, Ward-Paige, et al. 2010a, Nadon et al. 2012, leading to misrepresentations of the status of shark populations and their unfished baseline conditions (Heupel et al. 2009, Rizzari et al. 2014. Resale or republication not permitted without written consent of the publisherMar Ecol Prog SerTo address this problem, we explored whether dermal denticles, the small, tooth-like scales covering the skin of nearly all elasmobranchs ( Fig. 1), can be used as a tool to reconstruct shark communities on coral reefs. Denticles are several orders of magnitude more abundant than teeth on a living shark and are continually shed (Reif 1985a, Compagno et al. 2005. Like teeth, denticles preserve well and have a long fossil record (Janvier 1996, Sansom et al. 2012, po tentially providing a unique opportunity to retrospectively 'survey' modern and pre-exploitation shark assemblages. In this paper, we (1) review denticle morphology, taxonomy, and function; (...

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Global estimates of shark catches using trade records from commercial markets

Cited by 427 publications

References 29 publications

Reef-use and residency patterns of a baited population of silky sharks, Carcharhinus falciformis, in the Red Sea

Reef-use and residency patterns of a baited population of silky sharks, Carcharhinus falciformis, in the Red Sea

Evidence for rapid recovery of shark populations within a coral reef marine protected area

Dermal denticles as a tool to reconstruct shark communities

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