Depletion of trophy large-sized sharks populations of the Argentinean coast, south-western Atlantic: insights from fishers' knowledge

Irigoyen, Alejo Joaquín; Trobbiani, Gastón Andres

doi:10.1590/1982-0224-20150081

Cited by 27 publications

(17 citation statements)

References 53 publications

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“…Other top predator populations like sharks have no formal protection and its populations were reported to be decreasing. 57 The SJG food web was previously described using two distinct approaches: stable isotope analysis 58 and an Ecopath modelling. 59 Our results using a network approach match several results from these previous descriptions: the length of the food web (i.e.…”

Section: Discussionmentioning

confidence: 99%

Network Analysis Can Detect Changes In Food Web Stability Produced By Bottom Trawl Fishery In Patagonia

Funes

Saravia

Cordone

et al. 2022

Preprint

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Demersal fisheries are one of the top anthropic stressors in marine environments. In the long term, some species are more vulnerable to fishery impacts than others, which can lead to permanent changes on the food web. The trophic relationships between predator and prey constitute the food web and it represents a network of the energy channels in an ecosystem. In turn, the network structure influences ecosystem diversity and stability.The first aim of this study was to describe for the first time the food web of the San Jorge Gulf (Patagonia Argentina) with high resolution, i.e. to the species level when information is available. The San Jorge Gulf was subject to intense fisheries thus our second aim is to analyse the food web structure with and without fishery to evaluate if the bottom-trawl industrial fishery altered the network structure and stability. We used several network metrics like: mean trophic level, omnivory, modularity and quasi-sign stability. We included these metrics because they are related to stability and can be evaluated using predator diets that can weight the links between predators and prey. The network presented 165 species organized in five trophic levels. The inclusion of a fishery node adds 71 new trophic links. All weighted and unweighted metrics showed differences between the two networks, reflecting a decrease in stability when fishery was included in the system. Thus, our results suggested a probable change of state of the system. The observed changes in species abundances since the fishery was established, could represent the state change predicted by network analysis. Our results show how changes in the stability of food webs can be used to evaluate the impacts of human activity on ecosystems.

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Section: Discussionmentioning

confidence: 99%

Network Analysis Can Detect Changes In Food Web Stability Produced By Bottom Trawl Fishery In Patagonia

Funes

Saravia

Cordone

et al. 2022

Preprint

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“…40°–47°S) and seasonal occurrence to the north and south of this area (De Wysiecki et al ., 2020). Available abundance estimates show a declining trend in the SWA (Barbini et al ., 2015; Irigoyen & Trobbiani, 2016). Large individuals undertake northward breeding migrations to Río de la Plata ( c .…”

Section: Introductionmentioning

confidence: 99%

Growth estimates of young‐of‐the‐year broadnose sevengill shark, Notorynchus cepedianus, a top predator with poorly calcified vertebrae

Jaureguízar

Cortés

Braccini

et al. 2022

Journal of Fish Biology

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The broadnose sevengill shark, Notorynchus cepedianus (Péron, 1807), is a large marine top predator in temperate coastal ecosystems. Some aspects of its life history have been determined, but its growth pattern is yet to be fully understood. The authors used a multi-modelling approach and a sensitivity test to estimate growth parameters from young-of-year (YOY) length data collected off San Antonio Cape (SAC), Argentina, a critical habitat in the Southwest Atlantic Coastal Zone (SACZ).The best selected model, a sex-combined logistic growth model, estimated an asymptotic length (L ∞ ) of 92.58 cm TL (95% C.I.: 86.48-105.89 cm), a growth coefficient (K) of 0.006818 days À1 (95% C.I.: 0.004948-0.008777) and a size at birth (L 0 ) of 40.73 cm. The predicted annual growth (i.e., L 1 -L 0 ) was 43.2 cm TL. Males had smaller L 0 , higher K and achieved larger sizes after 1 year. The YOY in SAC attained a larger L 1 and grew faster than their Australian and South African wild counterparts.The consistent year-round presence of YOY in the SAC highlights the importance of this area as a pupping ground and potential nursery for N. cepedianus; this has direct implications for the allocation of research and management effort for the conservation of this species in the Southwest Atlantic.

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“…In light of current levels of global fisheries exploitation, estimates of contemporary Ne and demographic changes through time can provide valuable information to guide effective management and conservation of vulnerable elasmobranch species and populations [24][25][26] . As a coastal species, the ragged-tooth shark Carcharias taurus is not targeted by large off-shore fishing industries, but it is nonetheless threatened by small-scale fishing operations such as artisanal and recreational fisheries 27,28 . Population declines have been observed over much of the species' distribution, and the species is listed as critically endangered in South America 29 and East Australia 30 , and is thought to be locally extinct in the Mediterranean 31 .…”

Section: Introductionmentioning

confidence: 99%

A globally threatened shark,Carcharias taurus, shows no population decline in South Africa

Klein

Merwe

Dicken

et al. 2020

Preprint

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Knowledge about the demographic histories of natural populations helps to evaluate their conservation status, and potential impacts of natural and anthropogenic pressures. In particular, estimates of effective population size obtained through molecular data can provide useful information to guide management decisions for vulnerable populations. The spotted ragged-tooth shark Carcharias taurus (also known as the sandtiger or grey nurse shark) is widely distributed in warm-temperate and subtropical waters, but has suffered severe population declines across much of its range as a result of overexploitation. Here, we used multilocus genotype data to investigate the demographic history of the South African C. taurus population. Using approximate Bayesian computation and likelihood-based importance sampling, it was found that the population underwent a historical range expansion that may have been linked to climatic changes during the late Pleistocene. There was no evidence for a recent anthropogenic decline. Together with census data suggesting a stable population, these results support the idea that fishing pressure and other threats have so far not been detrimental to the local C. taurus 2 population. The results reported here indicate that South Africa could possibly harbour the last remaining, relatively pristine population of this widespread but vulnerable top predator.

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Depletion of trophy large-sized sharks populations of the Argentinean coast, south-western Atlantic: insights from fishers' knowledge

Cited by 27 publications

References 53 publications

Network Analysis Can Detect Changes In Food Web Stability Produced By Bottom Trawl Fishery In Patagonia

Network Analysis Can Detect Changes In Food Web Stability Produced By Bottom Trawl Fishery In Patagonia

Growth estimates of young‐of‐the‐year broadnose sevengill shark, Notorynchus cepedianus, a top predator with poorly calcified vertebrae

A globally threatened shark,Carcharias taurus, shows no population decline in South Africa

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