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Alicia Bertoloto Tagliolatto Daphne Wrobel Goldberg Matthew H. Godfrey Cassiano Monteiro‐Neto 《水产资源保护:海洋与淡水生态系统》2020,30(2):331-350
- Data on stranded sea turtles were examined between 2010 and 2016 along the northern region of Rio de Janeiro state and between 2016 and 2017 in the southern region, looking for spatio‐temporal patterns and determining which factors contributed to their mortality.
- A total of 12,162 strandings of all five species that occur in Brazil were recorded, with Chelonia mydas being the most common (89.9%). Sea turtles use the Rio de Janeiro coast as a feeding and/or migration area. The intense upwelling (October to April) may be an important factor for the sea turtles feeding in this region, mainly for Eretmochelys imbricata and Dermochelys coriacea, which had a higher number of strandings during this period.
- Areas further north of the study area include an important nesting site for Caretta caretta in Brazil, which explains the higher concentration of strandings of subadults/adults of this species in this region and during its nesting season.
- Many anthropogenic threats to sea turtles were documented, mainly incidental capture in fisheries and marine debris, indicating possible hotspots for these threats in the regions of Sepetiba and Guanabara Bays, Cabo Frio, and São Francisco de Itabapoana.
- Among the natural causes of strandings, the primary factors were chronic illness, endoparasites, and fibropapillomatosis. However, pollution may also be an indirect threat, which negatively affects these animals through reduced health and immunosuppression, leaving them more susceptible to opportunistic diseases.
- These data are valuable for directing and implementing specific and local mitigation measures along the Rio de Janeiro state coast, such as avoiding bycatch hotspots through fleet communication programmes and/or area and seasonal closures, enforceable legislation, effective penalties and proper waste management.
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Distribution and intensity of bottom trawl fisheries in the Patagonian Shelf Large Marine Ecosystem and its relationship with marine fronts 
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下载免费PDF全文 Trawling is a major concern worldwide and there is considerable debate about its impact on marine ecosystems. The Patagonian Shelf Large Marine Ecosystem (PSLME) is an important fishing area in the Southwest Atlantic where bottom trawling is the dominant fishing method. We investigated the distribution of bottom trawl fishing within this region, defining the areas of highest trawling intensity (hotspots) and evaluating their relationship with marine fronts. We focused on the three main oceanographic fronts, the shelf‐break front, the southern Patagonia front and the mid‐shelf front. To estimate fishing effort and trawled areas, we used VMS data from 2006 to 2012. Despite being almost a fully trawlable shelf, we found that the spatial distribution of trawling activity is patchy and trawling hotspots were small, comprising annually <5% of the shelf extension or <7% of the total trawlable area. Contrary to what is believed worldwide, our findings suggest that over the PSLME the magnitude of habitat effects as a result of bottom trawling is relatively small. Regarding the three frontal systems studied, only the shelf‐break front showed a positive relationship with trawl fishing activity. Although trawling hotspots did not overlap with marine fronts, the shelf‐break front receives more trawling effort than expected. We hypothesize that this pattern is due to aggregation of species near or at the front taking advantage of the opportunities provided by this area. 相似文献
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Donald A. Croll Heidi Dewar Nicholas K. Dulvy Daniel Fernando Malcolm P. Francis Felipe Galván‐Magaña Martin Hall Shawn Heinrichs Andrea Marshall Douglas Mccauley Kelly M. Newton Giuseppe Notarbartolo‐Di‐Sciara Mary O'Malley John O'Sullivan Marloes Poortvliet Marlon Roman Guy Stevens Bernie R. Tershy William T. White 《水产资源保护:海洋与淡水生态系统》2016,26(3):562-575
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Ryan Daly Denham Parker Geremy Cliff Gareth L. Jordaan Nkabi Nomfundo Rhett H. Bennett Bruce Q. Mann 《水产资源保护:海洋与淡水生态系统》2021,31(4):777-788
- The white-spotted wedgefish (Rhynchobatus djiddensis) is a Critically Endangered shark-like ray in the family Rhinidae. Throughout its Western Indian Ocean distribution, it is targeted for its valuable meat and fins and is reported to have undergone major population declines. However, there remains a need for species specific time-series data to accurately assess localized population declines.
- This study used two independent long-term (37 and 40 years) time-series catch data from competitive shore angling and shark nets to investigate the size composition and catch per unit effort (CPUE) and conduct a risk assessment for the population on the east coast of South Africa.
- From 1977 to 2017 the competitive shore fishery captured 7,703 individual R. djiddensis, whilst shark nets in the same region captured 2,856 individuals from 1981 to 2017. Individuals captured in the nets had a sex ratio of 1.8:1 females to males, and were larger than those caught by the anglers. Although the mean annual sizes of net-caught individuals were above the size of reported sexual maturity, there was little evidence to suggest that any individuals captured were reproductively active.
- Both the competitive shore fishery and shark net catches exhibited strong seasonal trends with the majority of R. djiddensis catches occurring from October to May peaking in austral summer. Standardized CPUE from the competitive shore fishery declined substantially between 1977 and 2017 and shark net catches exhibited a significant (p < 0.05) fourfold decline in annual nominal CPUE from 1981 to 2017.
- Ultimately, a risk assessment showed a 65.1% decline in abundance over a period of three generation lengths, which indicates that the sampled population of R. djiddensis in South Africa should be classified as Endangered according to the IUCN Red List using criterion A2b. The conservation implications of this are discussed.
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Natural mortality of Trachurus novaezelandiae and its size selection by purse seines off south‐eastern Australia 下载免费PDF全文
下载免费PDF全文 The natural mortality (M) and purse‐seine catchability and selectivity were estimated for yellowtail scad, Trachurus novaezelandiae, Richardson, a small inshore pelagic species harvested off south‐eastern Australia. Hazard functions were applied to two decades of data describing catches (mostly stable at a mean ± SE of 315 ± 14 t p.a.) and effort (declining from a maximum of 2,289 to 642 boat days between 1999/2000 and 2015/2016) and interdispersed (over 9 years) annual estimates of size at age (0+ to 18 years) to enable survival analysis. The data were best described by a model with eight parameters, including catchability (estimated at <0.1 × 10?7 boat/day), M (0.22/year) and variable age‐specific selection up to 6 years with a 50% retention among 5‐year‐olds (larger than the estimated age at maturation). The low catchability implied very low fishing mortality by the purse‐seine fleet. Ongoing monitoring and applied gear‐based studies are required to validate purse‐seine catchability and selectivity, but the data nevertheless imply T. novaezelandiae could incur additional fishing effort and, in doing so, alleviate pressure on other regional small pelagics. 相似文献
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Mingli Lin Francesco Caruso Mingming Liu Sovan Lek Kuan Li Rodolphe E. Gozlan Songhai Li 《水产资源保护:海洋与淡水生态系统》2020,30(4):860-867
- Based on optimal foraging theory, animals are expected to maximize foraging benefits whilst minimizing risks. Despite risking being subjected to anthropogenic impacts such as water contamination, marine traffic, and underwater noise, estuaries have been identified as the preferred habitat of the Indo‐Pacific humpback dolphin (Sousa chinensis, IPHD). However, it remains unclear why this vulnerable species favours such risky habitats.
- Here, an exploratory case study in Zhanjiang estuary, China, was conducted to test the hypothesis that IPHDs select estuarine habitats as a trade‐off that maximizes foraging opportunities whilst minimizing the risk of mortality.
- The results showed that IPHDs accept greater mortality risks for higher food rewards but select habitats with lower risks when food rewards are similar between two locations.
- Although this type of information is important for underpinning models for individual dolphins, its principal role is to show environmental protection agencies why IPHDs favour estuaries despite the increased mortality risks.
- Habitat conservation plans should carefully consider prey stocks, possibly through the presence of marine protected areas near estuaries, as local overfishing may lead vulnerable cetacean populations to take greater risks.