Catch composition and aspects of the biology of sharks caught by Thai commercial fisheries in the Andaman Sea

Catch composition, landing patterns and biological aspects of sharks caught by commercial fishing fleet operating in the Andaman Sea were recorded from landing sites in Ranong province of Thailand over a period of 1 year. Of the 64 species previously reported in the existing Thailand checklist, only 17 species were recorded in this study. Shark landings from the Andaman Sea appear now to be dominated largely by bamboo sharks Chiloscyllium spp. (Hemiscylliidae), which contribute c. 65% of the total number of sharks recorded. The carcharhinid sharks comprised c. 30·5% to the total catch, while the remaining c. 4·5% of landings comprised sharks from the families Squalidae, Stegostomatidae, Sphyrnidae and Triakidae. The catch composition is remarkably different from the previous landing survey in 2004, in that the current study found noticeable declines in landings of slow‐growing, late‐ maturing and low‐fecundity species (especially sphyrnid and carcharhinid species). The absences of many species and changes in life‐stage composition suggest that the populations of these groups may be close to collapse. The results from this study emphasize the urgency for additional research and monitoring efforts and also the need for management incentives in order to manage shark fisheries effectively in the Andaman Sea.     

Catch composition and reproductive biology of Sphyrna lewini (Griffith & Smith) (Carcharhiniformes, Sphyrnidae) in Indonesian waters

Data on the length compositions and reproductive biology have been collected for Sphyrna lewini in Indonesian waters, in which this species makes an important contribution to the biomass of its artisanal and small‐scale fisheries. These data were obtained by recording relevant body measurements and counts for this species while visiting Indonesian fish landing sites. The fish, which had been caught by gillnetting and longlining, covered a wide length range and included substantial numbers of immature, maturing and mature individuals. The vast majority of S. lewini <1100 mm total length (L_T) had been caught by gillnetting, whereas most of those above this length had been obtained through longlining. The number of embryos in pregnant females, which ranged from 14 to 41, with a mean of 25, was positively correlated with the L_T of those females. Birth occurred at c. 400 mm L_T and predominantly in October and November. The number of females was similar to that of males among smaller fish, but far greater than that of males among larger fish. This presumably reflects a faster growth and greater longevity of females, selectivity of longlining for females and a tendency for males to move outside the area fished. For males, the relationships between clasper length and the extent of its calcification, and also with sexual maturation and L_T have been determined. Females attained maturity (L_T50) at a far larger size (2285 mm) than males (1756 mm). The L_T of virtually all females and all males taken by gillnetting were less than their respective L_T50 at maturity, and c. 67 and 51% of the longline catches of females and males, respectively, were likewise immature. This feature, together with the substantial catches of S. lewini and the life cycle traits of elasmobranchs, suggest that this species is likely to be prone to overfishing in Indonesian waters. Furthermore, the removal of large numbers of this apex predator will presumably be affecting the trophic structure in the waters in which it is fished.     

Species and size compositions and reproductive biology of rays (Chondrichthyes, Batoidea) caught in target and non-target fisheries in eastern Indonesia

Extensive surveys of various fish landing sites in eastern Indonesia, conducted between April 2001 and March 2006, recorded a total of 54 species of batoid rays belonging to 12 families. The Dasyatidae was by far the most speciose family, comprising half of the recorded species, and was also the most abundant, contributing 89 and 44% to the total numbers and total estimated biomass of batoids, respectively. The size and sex compositions of 23 species of rays are described and an accurate size at maturity of males, i.e. with 95% CI, was determined for 13 of these species. The sex ratios were found to be close to parity in the majority of species, however, the landings of the whitespotted guitarfish Rhynchobatus australiae consisted of significantly more females than males, a situation also recorded for this species in the by-catch of the northern Australian prawn fishery. Data on aspects of the reproductive biology of three dasyatid species ( Dasyatis cf. kuhlii , Dasyatis zugei and Himantura walga ), which form a substantial component of the by-catch of the bottom trawl fisheries in the region, were collected on most sampling occasions. These small rays, i.e. maximum sizes 243–379 mm disc width, were found to have no distinct seasonal reproductive cycle and small litter sizes, i.e. less than four embryos. Opportunistic reproductive data, e.g. litter size and embryo sizes, were also collected from various other species. The litter sizes of the rhynchobatid and rhinobatid species examined were found to be larger than those of the gymnurid and dasyatid species examined, i.e. seven to 19 and two to 13 v. one to four, respectively. The data presented in this paper for the numerous species of rays which are landed by target and non-target fisheries in Indonesia represent the first such data for the vast majority of these species.     

New sharks of the genus Abdounia (Carcharhiniformes: Carcharhinidae) from the Upper Eocene of the Trans-Ural Region

Two new species of carcharhinid sharks from the Late Eocene deposits (Tavda Formation) of the southern Trans-Urals, Abdounia vassilyevae sp. nov., previously determined as A. aff. beaugei, and A. lata sp. nov., are described. To date, up to five Priabonian species of Abdounia have been recorded. New finds supplement the data on diversity, evolution, and paleobiogeography of Abdounia.     

Biological observations on the broadfin shark Lamiopsis temminckii (Carcharhiniformes: Carcharhinidae)

Biological information was collected from 214 individuals of the broadfin shark Lamiopsis temminckii measuring 418 to 1782 mm total length, L_T. Size at maturity (L₅₀) for females and males was estimated at 1430 and 1368 mm L_T, respectively, while mature and gravid females were observed from 1350 mm L_T with litter sizes 2–8 and size at birth 418–650 mm L_T. Analysis of stomach contents revealed a variety of prey, primarily crustaceans (54·0%), teleosts (42·7%) and cephalopods.     

Sampling mobile oceanic fishes and sharks: implications for fisheries and conservation planning

Tuna, billfish, and oceanic sharks [hereafter referred to as ‘mobile oceanic fishes and sharks’ (MOFS)] are characterised by conservative life‐history strategies and highly migratory behaviour across large, transnational ranges. Intense exploitation over the past 65 years by a rapidly expanding high‐seas fishing fleet has left many populations depleted, with consequences at the ecosystem level due to top‐down control and trophic cascades. Despite increases in both CITES and IUCN Red Listings, the demographic trajectories of oceanic sharks and billfish are poorly quantified and resolved at geographic and population levels. Amongst MOFS trajectories, those of tunas are generally considered better understood, yet several populations remain either overfished or of unknown status. MOFS population trends and declines therefore remain contentious, partly due to challenges in deriving accurate abundance and biomass indices. Two major management strategies are currently recognised to address conservation issues surrounding MOFS: (i) internationally ratified legal frameworks and their associated regional fisheries management organisations (RFMOs); and (ii) spatio‐temporal fishery closures, including no‐take marine protected areas (MPAs). In this context, we first review fishery‐dependent studies relying on data derived from catch records and from material accessible through fishing extraction, under the umbrella of RFMO‐administrated management. Challenges in interpreting catch statistics notwithstanding, we find that fishery‐dependent studies have enhanced the accuracy of biomass indices and the management strategies they inform, by addressing biases in reporting and non‐random effort, and predicting drivers of spatial variability across meso‐ and oceanic scales in order to inform stock assessments. By contrast and motivated by the increase in global MPA coverage restricting extractive activities, we then detail ways in which fishery‐independent methods are increasingly improving and steering management by exploring facets of MOFS ecology thus far poorly grasped. Advances in telemetry are increasingly used to explore ontogenic and seasonal movements, and provide means to consider MOFS migration corridors and residency patterns. The characterisation of trophic relationships and prey distribution through biochemical analysis and hydro‐acoustics surveys has enabled the tracking of dietary shifts and mapping of high‐quality foraging grounds. We conclude that while a scientific framework is available to inform initial design and subsequent implementation of MPAs, there is a shortage in the capacity to answer basic but critical questions about MOFS ecology (who, when, where?) required to track populations non‐extractively, thereby presenting a barrier to assessing empirically the performance of MPA‐based management for MOFS. This sampling gap is exacerbated by the increased establishment of large (>10000 km²) and very large MPAs (VLMPAs, >100000 km²) ‐ great expanses of ocean lacking effective monitoring strategies and survey regimes appropriate to those scales. To address this shortcoming, we demonstrate the use of a non‐extractive protocol to measure MOFS population recovery and MPA efficiency. We further identify technological avenues for monitoring at the VLMPA scale, through the use of spotter planes, drones, satellite technology, and horizontal acoustics, and highlight their relevance to the ecosystem‐based framework of MOFS management.     

Panbiogeographical analysis of the shark genus Rhizoprionodon (Chondrichthyes,Carcharhiniformes, Carcharhinidae)

The distributional patterns of the seven species of Rhizoprionodon were analysed using the panbiogeographical method of track analysis. The individual tracks of Rhizoprionodon suggest that the genus is mainly an Indian–Atlantic Ocean group. Five generalized tracks were found: (1) Caribbean, defined by R. porosus and R. terraenovae; (2) eastern coast of South America, defined by R. porosus and R. lalandei; (3) Indian Ocean, defined by R. acutus and R. oligolinx; (4) north‐western Australia, defined by R. acutus, R. oligolinx and R. taylori; (5) north‐north‐eastern Australia, defined by R. acutus and R. taylori. Only R. longurio was not included in any generalized track, and its distribution is restricted to the eastern Pacific Ocean. Two biogeographical nodes were found at the intersection of the generalized tracks 1 and 2 (Caribbean Sea) and generalized tracks 4 and 5 (north Australia). The generalized tracks overlap with those found in several unrelated marine taxa. Overall, the generalized tracks are associated with warm currents. The biogeographical nodes found (Caribbean and Australian) are coincident with the global distribution of mangroves.     

Virtual reconstruction of the skeletal labyrinth of two lamnid sharks (Elasmobranchii,Lamniformes)

The first virtual reconstruction of the skeletal labyrinth of the porbeagle shark Lamna nasus and the shortfin mako shark Isurus oxyrinchus is presented here using high‐resolution micro‐computed tomography. The results, in comparison with previously published information, suggest relationships between skeletal labyrinth morphology and locomotion mode in chondrichthyans, but also show that further studies are required to establish such connections. Nevertheless, this study adds to the knowledge of the skeletal labyrinth morphology in two apex elasmobranch species.     

Genetic identification of Carcharhinus sharks from the southwest Atlantic Ocean (Chondrichthyes: Carcharhiniformes)

Sharks of the genus Carcharhinus exhibit subtle morphological differences that are difficult to observe because of the common practice of head and fin removal, making species identification challenging. A total of 317 sharks, commonly called ‘cação‐baia’ (large individuals) or ‘machote’ (small size) in Brazil, were captured by the tuna fleet at the Santos and Guarujá fishery ports on the southeastern coast of Brazil and identified at the species level by multiplex PCR. The Internal Transcribed Spacer 2 region of ribosomal DNA was amplified using universal primers, and species‐specific primers were used for some of the Carcharhinus species. A total of 313 shark carcasses were directly identified by multiplex PCR. Four carcass samples did not amplify; therefore, the partial COI sequences were used to confirm their taxonomic identity. The results show that more than one species was being traded under the same commercial designation, including some Carcharhinus species that are under protection by federal legislation. Such species misidentification directly affects the long‐term sustainability of sharks.     

Dionchus postoncomiracidia (Monogenea: Dionchidae) from the skin of blacktip sharks, Carcharhinus limbatus (Carcharhinidae)

Postoncomiracidia of Dionchus sp. are described from specimens collected from the skin of 2 blacktip sharks Carcharhinus limbatus, captured in the northern Gulf of Mexico. The parasites resemble nonciliated oncomiracidia hatched from eggs laid by Dionchus sp. on gills of a cobia Rachycentron canadum and adults of Dionchus remorae that were collected from gills of a common sharksucker Echeneis naucrates, captured in association with a third blacktip shark. The hamuli of the postoncomiracidia were morphologically similar to those of adult D. remorae. This is the first report of dionchids from an elasmobranch and from a location other than the gills. These findings support the idea that some dionchid oncomiracidia colonize the skin of sharks or other aquatic vertebrates that sponsor remoras, prior to transferring to other remoras and maturing.     

Size and distribution of Pandarus satyrus (Copepoda: Pandaridae) on the blue shark Prionace glauca (Carcharhiniformes: Carcharhinidae) in Costa Rica.

A total of 80 specimens of Pandarus satyrus, a cosmopolitan ectoparasitic copepod, were taken from fishery catches of blue sharks (Prionace glauca) in the Eastern Pacific coast of Costa Rica. All specimens were found in the dorsal surface of pectoral fins (8-30 per shark). Longer specimens were most abundant.     

Two new species of Paraorygmatobothrium (Cestoda: Tetraphyllidea) from weasel sharks (Carcharhiniformes: Hemigaleidae) of Australia and Borneo

Two new species of Paraorygmatobothrium Ruhnke, 1994, P. janineae n. sp. and P. kirstenae n. sp., are described from the spiral intestine of 2 shark species of the Family Hemigaleidae: Hemigaleus microstoma and Hemipristis elongata. The 2 new cestode species differ from other members of Paraorygmatobothrium in vitelline follicle distribution and possession of a cephalic peduncle. The 2 new species differ from 1 another in total length, maximum width, scolex size, number of proglottids per strobila, and number of testes per proglottid. The generic diagnosis of Paraorygmatobothrium is emended to include the new species. The results of this study extend the distribution of Paraorygmatobothrium to include the carcharhinid shark family Hemigaleidae.     

Reproductive biology of the swell shark Cephaloscyllium ventriosum (Carcharhiniformes: Scyliorhinidae)

The Cephaloscyllium ventriosum shark is present in the artisanal fisheries of elasmobranchs on the western coast of Baja California Sur, Mexico. The main characteristics of the sexual maturation of this species based on individuals captured from off north-west Mexico in 2013–2016 are described. The size at maturity of this species was determined for the first time (total length 82 cm for females and 76 cm for males). Most females had one egg case per one uterus, and two per one uterus was an isolated event of low incidence. From the histological analysis of females, it was possible to show sperm storage in the oviducal gland. Fully developed sperm in immature organisms were identified in the testes. The main indicator of the maturity stage of males and their mating activity is the clasper. The present study provides evidence for a reliable estimation of the sexual maturity of these organisms, demonstrating the need for the combination of macroscopic and microscopic methods.     

Age group DNA methylation differences in lemon sharks (Negaprion brevirostris): Implications for future age estimation tools

Age information is often non‐existent for most shark populations due to a lack of measurable physiological and morphological traits that can be used to estimate age. Recently, epigenetic clocks have been found to accurately estimate age for mammals, birds, and fish. However, since these clocks rely, among other things, on the availability of reference genomes, their application is hampered in non‐traditional model organisms lacking such molecular resources. The technique known as Methyl‐Sensitive Amplified Polymorphism (MSAP) has emerged as a valid alternative for studying DNA methylation biomarkers when reference genome information is missing, and large numbers of samples need to be processed. Accordingly, the MSAP technique was used in the present study to characterize global DNA methylation patterns in lemon sharks from three different age groups (juveniles, subadults, and adults). The obtained results reveal that, while MSAP analyses lack enough resolution as a standalone approach to infer age in these organisms, the global DNA methylation patterns observed using this technique displayed significant differences between age groups. Overall, these results confer that DNA methylation does change with age in sharks like what has been seen for other vertebrates and that MSAP could be useful as part of an epigenetics pipeline to infer the broad range of ages found in large samples sizes.     

Mites of the genus Holostaspella (Acari: Gamasida: Macrochelidae) in Indonesia

The genus Holostaspella of the family Macrochelidae consists of more than 30 species. Of these, seven species have been recorded from Indonesia. In the present study, we review the genus in Indonesia, record two species ( H. pulchella and H. similiornata ) for the first time from Indonesia, and describe two new species ( H. oblonga n. sp. and H. villosa n. sp.) on the basis of the specimens collected in Java and Sulawesi. A key to the species of the genus in Indonesia is also provided.     

Catch composition,reproductive biology and diet of the bramble shark Echinorhinus brucus (Squaliformes: Echinorhinidae) from the south‐eastern Arabian Sea

Fishery and biological data are presented for the poorly known bramble shark Echinorhinus brucus (Squaliformes: Echinorhinidae), from the deep waters of the south‐eastern Arabian Sea. A total of 5318 individuals from by‐catch landings of deep‐water bottom set longlines, gillnets and shrimp trawl fisheries operating at depths of 200–1200 m were recorded between January 2008 and December 2011 at the Kochi Fisheries Harbour (Kerala). A total of 431 individuals, from 46 to 318 cm total length (L_T) and 0·8 to 132 kg total mass (M_T), were examined to determine biological data for this species. The L_T at which 50% were mature (L_T50) for females and males was estimated at 189 and 187 cm L_T. Litter size ranged from 10 to 36 and size at birth was between 42 and 46 cm L_T. Dietary analysis of stomach contents revealed E. brucus feeds on a variety of prey including crustaceans (69% index of relative importance, I_RI), teleosts (25·8% I_RI), cephalopods (1·7% I_RI) and elasmobranchs (0·7% I_RI). This study provides the first detailed biological data for this species and also highlights the extent of the by‐catch fishery for this species in Indian waters.     

Considerations on the diet composition and feeding rate of dermersal sharks in 15 European public aquaria

To get an overview of the feeding practices applied to dermersal sharks in captivity, a questionnaire was sent to 15 European public aquaria. The most common dermersal shark species kept in the participating aquaria are Carcharhinus plumbeus (n=9), Carcharias taurus (n=7), and C. melanopterus (n=6). Body weight (BW) was calculated using captive estimated body length (BL) and actual weight data obtained from commercial fisheries. The estimated BW for C. plumbeus in all participating aquaria is higher than the calculated BW. The feeding rate (FR) for adult C. plumbeus varied widely within participating aquaria (2.3–11.5% BW_cal/week or 32–112 kcal/kg BW_cal/week). The FR for adult C. plumbeus was lower (1.2–7.9% BW_est/week or 17–99 kcal/kg BW_est/week) using the estimated BW. Adult Carcharias taurus were fed at 1.3–5.0% BW_cal/week or 70–170 kcal/kg BW_cal/week. Negaprion brevirostris was fed at 5.0% BW_est/week or 57 kcal/BW_est/week. The relationship between FR and estimated BW is expressed as FR=54.5 e^?0.033BW. In this study, the feeding frequency for C. plumbeus varied between 1–7 times a week, with an average of 3.3 times a week. Diet in all aquaria consisted of both lean and fatty fish, and sometimes squid or crustaceans. Supplementation of vitamins is common practice in 80% of the surveyed aquaria, although a wide variety of quantity and quality was observed. Ten aquaria (66%) add iodine, as potassium iodide (0.4–12.5 mg KI/kg BW/week) or calcium‐iodate (322–1,500 mg/kg food/week), to their food. Zoo Biol 22:203–226, 2003. © 2003 Wiley‐Liss, Inc.     

Species composition and aspects of the biology of Orectolobiformes from Indonesian waters

The biological aspects of members of the order Orectolobiformes exploited in Indonesian waters are given. Seven species belonging to five families were recorded in the catches at various landing sites in southern Indonesia. Of these, Chiloscyllium punctatum was the most abundant species landed, contributing >50% of the number of orectolobiforms recorded. The biological data obtained varied greatly between the species listed. The total length (L_T) at maturity for some species, e.g. C. punctatum and Nebrius ferrugineus, varied from that which has been previously recorded for those species in other regions. This highlights the need for regional‐specific biological data for fisheries managers and conservation assessors.     

Everyday Politics of (In)formal Marital Dissolution in Cambodia and Indonesia

Placing contemporary marriage and its dissolution at its heart, this paper explores rural women's experiences of customary and legal unions in Cambodia and Indonesia. We contend that women's navigation in-between ‘informal’ ethics and morals versus ‘formal’ state-sponsored legal doctrine constitute a form of ‘everyday politics’ that has been unduly neglected. Critiquing the taken-for-granted nature of marriage in academic scholarship, we show how the axiomatic notion that marriage registration is inherently beneficial to women is complicated by the nonlinear and mobile trajectories of conjugality in our two case study communities. In turn, we call for marriage and its breakdown to receive more sustained and nuanced analysis as the primary unit of Southeast Asian life.