Reducing elasmobranch bycatch: Laboratory investigation of rare earth metal and magnetic deterrents with spiny dogfish and Pacific halibut

Spiny dogfish (Squalus acanthius) comprises a significant unwanted bycatch on demersal longlines set for halibut and cod in shelf waters of the east and west coasts of North America. In this laboratory study, attacks on baits were tested in the presence of two different rare earth materials (neodymium–iron–boride magnets and cerium mischmetal) believed to deter elasmobranch catch. Experiments were made with spiny dogfish and with Pacific halibut (Hippoglossus stenolepis) in pairwise tests of the rare earth materials and inert metal controls. Dogfish attacked and consumed baits tested with cerium mischmetal at a lower frequency than controls. Times to attack the baits were significantly higher in the presence of mischmetal, as were numbers of approaches before first attack. The time differential between mischmetal and control treatments and the number of baits consumed converged with increasing food deprivation (1 h, 2 d, and 4 d), but treatment differences were always significant. Cerium mischmetal appeared to be irritating to dogfish and may disrupt their bait detection and orientation abilities. Magnets also appeared to irritate dogfish but provided no protection for baits in feeding trials. Pacific halibut showed no reaction whatsoever to the rare earth magnets or cerium mischmetal. Mischmetal, therefore, may be useful in reducing spiny dogfish bycatch in the halibut fishery. Disadvantages in using mischmetal in commercial operations are expense, hazardous nature, and relatively rapid hydrolysis in seawater.     

Gillnet selectivity of small coastal sharks off the southeastern United States

Gillnet selectivity parameters for the Atlantic sharpnose, Rhizoprionodon terraenovae, blacknose, Carcharhinus acronotus, finetooth, Carcharhinus isodon, and bonnethead, Sphyrna tiburo, sharks were estimated from fishery-independent catches in multi-panel gillnets with stretched mesh sizes ranging from 8.9 to 14.0 cm in steps of 1.3 cm, with an additional size of 20.3 cm. Mesh selectivities were estimated using a maximum-likelihood model, which fits a gamma distribution to length data for each mesh size using the log-likelihood function. The Atlantic sharpnose and finetooth shark exhibited the broadest selection curves. Peak selectivities for the Atlantic sharpnose were reached from 750 mm FL for the 8.9 cm mesh to 1150 mm FL for the 14.0 cm mesh in 50 mm FL increments per mesh. Peak selectivity for the finetooth shark was reached at 550 mm FL for the 8.9 and 10.2 cm meshes, increased to 650 mm FL for the 11.4 mesh, and 750 mm FL for the 12.7 and 14.0 cm meshes. Selectivity was highest at 1150 mm FL for the 20.3 cm mesh. The bonnethead and blacknose shark exhibited narrower selection curves, with peak selectivity occurring at 450 mm FL for the 8.9 cm mesh, 750 mm for the 12.7 cm mesh in 100 mm FL increments per mesh. Maximum selectivity for the 20.3 cm mesh was 950 and 1050 mm FL for bonnethead and blacknose shark, respectively. The θ₁ values for blacknose and finetooth shark were most similar (140.58 and 141.25), whereas the value calculated for Atlantic sharpnose was the highest (211.95) and that for the bonnethead (131.77) was the lowest. Values calculated for θ₂, a parameter that describes the variance of sizes by mesh, ranged from 27,259 for the bonnethead to 189,873 for the finetooth shark. Although gillnets used in this study were not directly constructed for use in estimation of gillnet selectivities, information on mesh selectivities estimated herein has direct applicability to commercial gillnets with meshes of similar sizes.     

鲨鱼皮微电铸复制工艺研究

采用微电铸技术对生物表面形貌进行直接复制以成形出与生物原型形貌相接近的仿生表面,是生物复制成形技术由高聚物成形向金属沉积成形扩展的新途径。以鲨鱼皮为生物模板,针对其表皮微形貌结构特征,通过倾斜溅射方式先在其鳞片表面沉积导电层,进而采用正负间断脉冲电流对鲨鱼皮生物模板进行微电铸复制,成形出鲨鱼皮微电铸模板及仿鲨鱼表面。复制精度分析结果表明,采用微电铸生物复制成形工艺可以实现对鲨鱼皮外端沟槽微形貌的高逼真复制,证明该工艺可以应用于微尺度、复杂生物表面形貌的直接复制。     

Demographic analysis of the night shark (Carcharhinus signatus, Poey, 1868) in the equatorial Southwestern Atlantic Ocean

A demographic analysis of the night shark (Carcharhinus signatus) was carried out to establish the conservation status of this species caught by longlines on oceanic banks off northeastern Brazil. The biological input parameters (age at first maturity, longevity, fecundity and natural mortality) used for the construction of life tables were taken randomly from their respective probability distributions, taking into account the uncertainty of the parameter estimates by employing Monte Carlo simulations. Nine scenarios were generated from natural (M), total (Z), initial (Z₀—corresponding to the first year of life of the cohort) and population equilibrium (Z′) mortality rates. Each scenario was executed 1000 times, varying the vital input rates for the estimation of the demographic parameters (net reproductive rate, R₀; mean generation length, G; and intrinsic rate of population increase, r). Age at first maturity for C. signatus is 10 years; 89.2% of the stock is made up of juveniles, with fishery recruitment beginning at 5 years of age. The scenarios reveal that catches prior to first sexual maturity result in a significant reduction in population (−8.1%/year) and that the population would only support current efforts if the individuals caught are over 10 years of age or if mortality due to fishing efforts corresponded to the equilibrium rate beginning with recruitment at 5 years of age. A low survival rate is estimated for the first year of life. In order for the population to remain in equilibrium with current mortality rates and recruitment age, survival should be around 0.9. The combination of a low initial survival rate, low fecundity, fishery efforts and the large number of juveniles caught indicates that the C. signatus population off northeastern Brazil is being overexploited.     

Aquaculture Biotechnology,by Garth L. Fletcher,Matthew L. Rise,and Wiley-Blackwell

FOOD MICROBIOLOGY: FUNDAMENTALS AND FRONTIERS, Second Edition. Edited by Michael P. Doyle, Larry R. Beuchat, and Thomas J. Montville. Washington, DC, ASM Press, 2001, 888 pages. $124.95. Reviewed by Keith W. Gates.     

中国鱼翅消费与鲨鱼捕捞关系初步研究

近年来,鲨鱼资源养护和管理成为国际社会关注点,中国的鱼翅消费被认为是破坏鲨鱼资源的罪魁祸首。为了解事实,采用问卷调查法于2017年对中国鲨鱼产品主要批发市场(北京、上海、广州)的商户进行调查。结果显示:经营种类以鱼翅为主;鱼翅销量和价格的最高峰阶段为2008—2012年,2013年开始,销量和价格均急剧下降,最低峰阶段为2015—2016年,且2017年较2016年相比,销量和价格继续下跌; 60%的商户反映经营状况不佳。海关数据表明,中国内地干鱼翅进口量由2004年的最高峰4 776 t降到2012年的108 t,且2013—2016年持续下降。而联合国粮农组织(FAO)发布的数据显示全球鲨鱼捕捞量在2013—2016年整体平稳,全球鲨鱼捕捞量并未随中国鱼翅消费的下降而下降。故把中国消费鱼翅作为破坏鲨鱼资源的罪魁祸首是失实的。     

Potential impacts of emerging mahi-mahi fisheries on sea turtle and elasmobranch bycatch species

Mahi-mahi (Coryphaena hippurus) is a resilient pelagic species that could provide long-term highly productive fisheries. Using FAO data we document enormous increases (746%) in reported global mahi-mahi landings since 1950. Detailed mahi-mahi fisheries records are limited, but an observer program monitoring Costa Rica’s Pacific mahi-mahi pelagic longline fleet between 1999 and 2008 (n = 217 sets) provided a rare opportunity to quantify bycatch in these fisheries. Several sea turtles and sharks of global conservation concern were caught incidentally: olive ridley turtle (Lepidochelys olivacea; n = 1348, mean = 9.05 per 1000 hooks), silky shark (Carcharhinus falciformis; n = 402, mean = 2.96 per 1000 hooks), thresher sharks (Alopias sp.; n = 158, mean = 1.12 per 1000 hooks), green turtle (Chelonia mydas; n = 49, mean = 0.35 per 1000 hooks), and three other threatened sharks in small numbers. Pelagic stingray (Pteroplatytrygon violacea; a ray of low conservation concern) was also a common bycatch (n = 625, mean = 4.77 per 1000 hooks). Generalized linear models (GLMs) of catch rates showed increases in olive ridley turtles and decreases in mahi-mahi and silky sharks over the decade examined. The high hooking survival rates of olive ridley and green turtles in observed sets (95% and 96% respectively) suggest that widespread training of the fleet in careful gear removal and turtle release methods could be one effective bycatch mitigation strategy for these species. GLMs also provide evidence that closing the fishery during peak olive ridley nesting times (at least near nesting beaches), in combination with reduced gear soak times, could help minimize the fishery’s impacts on threatened bycatch species while still maintaining a productive fishery.     

Effects of tourism-related provisioning on the trophic signatures and movement patterns of an apex predator, the Caribbean reef shark

Wildlife provisioning, i.e. the provision of bait to generate aggregations of charismatic megafauna as tourist attractions, occurs around the world. This practice is often promoted as an economic incentive to conserve the focal species, yet has stimulated debate based on the potential for risks to human safety and perceptions of behavioural shifts in provisioned populations. We studied a population of Caribbean reef sharks (Carcharhinus perezi) in the Bahamas that has been subject to regular provisioning for >20 years. We used a combination of focal observations of sharks during feeding events, remote acoustic telemetry and stable isotope analysis of shark muscle tissue to determine the impacts of provisioning on the trophic signatures and ranging behaviour of sharks in this population. A small number of large sharks monopolised more than 50% of the bait on offer. These ‘fed’ individuals showed significant ¹⁵N enrichment in their tissues compared to conspecifics of the same size that failed to obtain bait at the feeding site, and un-provisioned sharks from a control site. Despite the disparity in trophic signatures, fed, unfed and control sharks exhibited similar degrees of residency at their respective home receiver sites, and travelled similar daily minimum distances. Thus, despite long-term provisioning of this Caribbean reef shark population, there is no evidence for shifts in the behaviours considered which might affect the ecological role of these sharks. However, further research is required to examine potential indirect effects of shark provisioning on sympatric fauna and habitat before this activity can be placed within a sustainable marine conservation framework.     

Identification and Biological Characterization of Angiogenic and Tumor Growth Inhibitors derived from Sinica cetorhinus maximum Cartilage

Shark (Sinica cetorhinus maximum) cartilage was extracted in 1 mol/L Gu- HCl guanidine. Two purified active proteins with apparent molecular weights of 15.2×10³ Da and 8.0×10³ Da (designated as Sp15 and Sp8, respectively) were obtained through ultrafiltration and Superdex 75 chromatography. The activities of the samples were studied in terms of their potential inhibition of vascular endothelial cell growth in vitro, of angiogenesis both in rabbit cornea and chick embryo chorioallantoic membrane (CAM) assay models in vivo, and of growth of transplanted S180 sarcoma in mice in vivo. The results showed that Sp15 expressed a typical lysozymatic activity up to 223,000 U/mg and its N-terminus was highly homologous to lysozymes of various mammalian origins. Sp15 exhibited a strong anti-angiogenic activity only in vitro, whereas Sp8 shared this effect both in vitro and in vivo. Both Sp15 and Sp8 provided an effective anti-tumor activity in mice bearing transplanted S180 sarcoma. These results suggest that Sp15 is a shark cartilage-derived lysozyme that participates in the defense to bacterial invasion to the body, while Sp8 is an angiogenic inhibitor that mediates at least part of the anti-tumor activity associated with shark cartilage probably through the inhibition of tumor-induced angiogenesis.