A New Inland Record of the Bull Shark Carcharhinus leucas (Müller & Henle 1839) from Peninsular Malaysia

A single specimen of a bull shark Carcharhinus leucas (Müller & Henle 1839) with c. 102 cm of total length was landed and photographed on 25 March 2019 in Sungai Mawai Lama, about 25 km inland, Kota Tinggi District, Johor, Peninsular Malaysia. This rare finding represents only the second record of C. leucas in inland Peninsular Malaysia. This shark was identified as C. leucas by the snout much shorter than the width of mouth and bluntly rounded, first dorsal fin triangular, rearward sloping, originating over or slightly behind pectoral insertion, second dorsal fin much smaller than the first dorsal fin (< 3.1:1), and lack of an interdorsal ridge. The coloration of fresh specimen: greyish back and white belly, the dark coloration on the tip of the caudal fins and second dorsal fin. This species is currently listed as a vulnerable species based on the IUCN Red List Status. Further study and monitoring are needed to assess the possibility of the importance of Sungai Mawai Lama as critical habitat of C. leucas.

Residency of bull sharks, Carcharhinus leucas (Carcharhiniformes: Carcharhinidae), at San Pedrillo Islet in Islas Murciélago, North Pacific of Costa Rica

Introduction: The bull shark, Carcharhinus leucas, is particularly vulnerable to anthropogenic actions because of its permanence in coastal ecosystems; populations depletion is registered in different places around the world. Aggregations of bull sharks have been reported in the North Pacific of Costa Rica, at Islas Murciélago, within the Guanacaste Conservation Area. Objective: To study the residency of bull sharks at San Pedrillo islet, Islas Murciélago. Methods: During the study period (June 2013 to February 2015) we used passive telemetry to tag 10 bull sharks. Results: All the sharks tagged were females, they were detected on 59 798 occasions by the acoustic receiver deployed in San Pedrillo. Acoustic signals from tagged sharks were received for a total period of 1 to 229 days (mean = 73.9 ± 71.3 days), with the last detections occurring on 9 January 2015. The Residency Index for each tagged shark across the entire monitoring period ranged from 0.41 to 1.00. The bull shark activity showed a significant pattern throughout the day at the receiver that specifically corresponded with the daily light cycle. Conclusions: This study concludes that San Pedrillo is an aggregation site (cleaning station) for bull sharks (C. leucas), possibly related to reproduction and not feeding behaviors.

Fishing for survival: importance of shark fisheries for the livelihoods of coastal communities in Western Ghana

Small-scale shark fisheries support a large number of coastal community livelihoods in developing countries. Shark meat comprises a cheap source of protein and is traded locally in many parts in developing countries, while the skins, oil, fins and gill rakers are exported to the international market. This study addresses a gap in literature regarding the importance of elasmobranchs to key shark-fishing communities and the degree to which trade in shark products (meat and fins) vary in time and among fishing communities in Ghana. We interviewed 85 fishers and traders involved in shark fisheries in Axim, Dixcove, and Shama communities using semi-structured questionnaires. Fishing was the primary source of income and accounted for 59.9% of the total household income of respondents. Other important economic activities were fish processing (15.2%), fish retailing (14.8%), and small businesses (2.9%). One-third and often two-thirds of respondents generated between 80-100% of their income from shark fisheries: Axim (n = 65%), Dixcove (68%), and Shama (35%). Shark meat consumption was common among fishers and traders and represents a substantial source of protein in the diet of the study communities. Overexploitation of these species may compromise food security. Hammerhead Sharks (Sphyrna spp) and Bull Shark (Carcharhinus leucas) have the most valuable fins and meat. Further, 75% and 95% of fishers and traders respectively see fishing and trading of shark meat as their last safety-net and, therefore, tend to be satisfied with their jobs. Non-fishing related livelihood streams including small businesses and transportation were the major fallback activities both fishers and traders preferred to rely on if there is a ban on the exploitation of sharks in Ghana. Thus, any shark management strategy must take into consideration the preferred livelihood fallback options outlined by fishers and traders, and implement them to ensure the success of the intervention.

Insights Into Insular Isolation of the Bull Shark, Carcharhinus leucas (Müller and Henle, 1839), in Fijian Waters

The bull shark (Carcharhinus leucas) is a large, mobile, circumglobally distributed high trophic level predator that inhabits a variety of remote islands and continental coastal habitats, including freshwater environments. Here, we hypothesize that the barriers to dispersal created by large oceanic expanses and deep-water trenches result in a heterogeneous distribution of the neutral genetic diversity between island bull shark populations compared to populations sampled in continental locations connected through continuous coastlines of continental shelves. We analyzed 1,494 high-quality neutral single nucleotide polymorphism (SNP) markers in 215 individual bull sharks from widespread locations across the Indian and Pacific Oceans (South Africa, Indonesia, Western Australia, Papua New Guinea, eastern Australia, New Caledonia, and Fiji). Genomic analyses revealed partitioning between remote insular and continental populations, with the Fiji population being genetically different from all other locations sampled (FST = 0.034–0.044, P &lt; 0.001), and New Caledonia showing marginal isolation (FST = 0.016–0.024, P &lt; 0.001; albeit based on a small sample size) from most sampled sites. Discriminant analysis of principal components (DAPC) identified samples from Fiji as a distinct cluster with all other sites clustering together. Genetic structure analyses (Admixture, fastStructure and AssignPOP) further supported the genetic isolation of bull sharks from Fiji, with the analyses in agreement. The observed differentiation in bull sharks from Fiji makes this site of special interest, as it indicates a lack of migration through dispersal across deep-water trenches and large ocean expanses.

Metabarcoding Gillnets to Assess Unaccounted Catch Depredation or Escape

Gillnets are the world’s most common net-based fishing gear, comprising walls of light mesh designed to entangle fish. Like all fishing gears, gillnets are not 100% effective for the targeted catches, and usually catch similar-sized, unwanted animals that are discarded, often dead. Gillnets are often retrieved with holes in the netting, which means some animals escape or are depredated unseen, but with some mortality. To effectively manage fisheries around the world, information is required on not only the harvested and discarded mortalities, but also problematic interactions and mortalities caused by the fishing gear and especially those involving protected species. This study sought to assess a novel method for determining such interactions by sampling pieces of netting around holes in polyethylene gillnets for environmental deoxyribonucleic acid or ‘eDNA’. Here we show that eDNA correctly identified all previously entangled-and-landed species. Also, eDNA from three uncaptured taxa were recorded: bull shark, Carcharhinus leucas, white shark, Carcharodon carcharias and dolphins (Delphindae), illustrating the potential to reveal previously cryptic gillnet interactions. We propose that as scientific methods evolve and autonomous real-time DNA surveillance becomes routine, eDNA testing of fishing gears and vessels could provide a novel, complementary fishery-monitoring tool.