V. Jaiteh

Combining in-trawl video with observer coverage improves understanding of protected and vulnerable species by-catch in trawl fisheries

Assessments of incidental wildlife mortality resulting from fishing rarely account for unobserved by-catch. We assessed by-catch of protected and vulnerable wildlife species in an Australian trawl fishery by comparing in-trawl video footage with data collected by an on-board observer. Data were obtained from 44 commercial trawls with two different by-catch reduction devices (BRDs). Eighty-six individuals from six major taxa (dolphins, sharks, rays, sea snakes, turtles and sygnathids) were documented from video analysis, including the endangered scalloped hammerhead shark (Sphyrna lewini) and the critically endangered green sawfish (Pristis zijsron). On the basis of the 2008–2009 fishing effort of 4149 trawls and scaling from these results, we estimated the annual catch of protected and vulnerable species (± 1 s.e.) at 8109 ± 910 individuals. Only 34% of by-catch was expelled through the BRDs. Independent observer data for the 44 trawls showed that 77% of the landed by-catch from these taxa were dead when discarded. The results indicate that unaccounted by-catch in trawl fisheries can be substantial, and that current methods of recording by-catch on-board vessels are likely to underestimate total fishing mortality. We recommend gear modifications and their validation through dedicated observer coverage, combined with in-trawl video camera deployments to improve current approaches to by-catch mitigation.

Higher Abundance of Marine Predators and Changes in Fishers’ Behavior Following Spatial Protection within the World’s Biggest Shark Fishery

Fisheries are complex social-ecological systems, where managers struggle to balance the socio-economic interests of fishing communities with the biology and ecology of fisheries species. Spatial closures are a popular measure to address conservation and fisheries management goals, including the protection of shark populations. However, very little research has been published on the effectiveness of shark-specific closures to protect sharks, or their impacts on fisher behavior. Situated within the global center of tropical marine biodiversity, Indonesia’s shark fishery contributes more to the international shark fin trade than any other nation. Here we evaluate the effect of shark-specific closures on sharks and other species of interest, as well as shark fishers’ responses to losing access to their former fishing grounds. We assessed shark diversity and abundance in an open access zone (OAZ) and two No-Take Zones (NTZs) of a Marine Protected Area within the recently established shark sanctuary in Raja Ampat, Indonesia, where sharks have high monetary value as a tourism attraction. Shark abundance was significantly higher in the privately managed NTZs than in the OAZ. Across all management zones, neither zone size, depth nor reef complexity explained variations in shark abundance, suggesting that governance is the main driver of successful shark conservation areas. These trends were also reflected in species targeted by small-scale reef fisheries, including snappers, emperor, groupers, tunas, mackerels, and large-bodied wrasse and parrotfish. Interviews with shark fishers who lost access to their primary fishing grounds when the shark sanctuary was established showed that while most fishers (88%) knew that sharks were protected in Raja Ampat, many were unsure about the purpose of the sanctuary. Few fishers felt that the agencies implementing fishing bans understood their livelihood needs. We found that shark fishers adapted to the loss of former fishing grounds by shifting fishing effort to other locations or diversifying their livelihoods, including illegal petrol transport. While conserving sharks for tourism can be effective, it may inadvertently result in displacing fishing effort to unprotected regions. We propose that effective shark conservation in Indonesia will need to combine strategic spatial protection with efforts to support livelihood security and diversification.

Predators in danger: shark conservation and management in Australia, New Zealand and their neighbours

In this chapter we examine the biodiversity and the status of conservation and management of shark species in Australasia and Indonesia. Almost 17% of shark species in the region are listed by the International Union for the Conservation of Nature (IUCN) as threatened, and approximately 40% are of conservation concern, their future being dependent on the implementation of appropriate management strategies. Overfishing is a major threat to sharks, as their life-history strategies make them susceptible to even modest levels of fishing mortality. In Australia and New Zealand many shark stocks experienced dramatic declines as a consequence of overfishing; however, in the past few decades substantial improvements in the management of shark fisheries have taken place. On the other hand, shark fishing in Indonesia is largely unreported and unregulated and fishing by Indonesian vessels is likely to have consequences that go beyond the depletion of local populations, affecting shark populations in neighbouring countries such as Australia. We illustrate examples of over fishing in the region, discuss the potential effects of habitat degradation and climate change in the future and examine current management frameworks for the conservation of shark species in the region with an emphasis on the implementation of Nation Plans of Action for the Conservation and Management of Sharks (NPoAs).

Genetic structure and signatures of selection in grey reef sharks (Carcharhinus amblyrhynchos)

With overfishing reducing the abundance of marine predators in multiple marine ecosystems, knowledge of genetic structure and local adaptation may provide valuable information to assist sustainable management. Despite recent technological advances, most studies on sharks have used small sets of neutral markers to describe their genetic structure. We used 5517 nuclear single-nucleotide polymorphisms (SNPs) and a mitochondrial DNA (mtDNA) gene to characterize patterns of genetic structure and detect signatures of selection in grey reef sharks (Carcharhinus amblyrhynchos). Using samples from Australia, Indonesia and oceanic reefs in the Indian Ocean, we established that large oceanic distances represent barriers to gene flow, whereas genetic differentiation on continental shelves follows an isolation by distance model. In Australia and Indonesia differentiation at nuclear SNPs was weak, with coral reefs acting as stepping stones maintaining connectivity across large distances. Differentiation of mtDNA was stronger, and more pronounced in females, suggesting sex-biased dispersal. Four independent tests identified a set of loci putatively under selection, indicating that grey reef sharks in eastern Australia are likely under different selective pressures to those in western Australia and Indonesia. Genetic distances averaged across all loci were uncorrelated with genetic distances calculated from outlier loci, supporting the conclusion that different processes underpin genetic divergence in these two data sets. This pattern of heterogeneous genomic differentiation, suggestive of local adaptation, has implications for the conservation of grey reef sharks; furthermore, it highlights that marine species showing little genetic differentiation at neutral loci may exhibit patterns of cryptic genetic structure driven by local selection.

First records of the grey nurse shark Carcharias taurus (Lamniformes: Odontaspididae) from oceanic coral reefs in the Timor Sea

The threatened grey nurse shark (Carcharias taurus) is reported for the first time from oceanic coral reefs in the Timor Sea. Generally known from temperate and subtropical coastal reef habitats, this species was encountered by Indonesian traditional fishers on oceanic coral reefs in an area of the Australian Exclusive Economic Zone known as the 1974 MoU Box, some 200 km from the Australian mainland. The presence of C. taurus on these remote tropical reefs bears important management implications, including the species’ protected status in Australian waters and the challenges of regulating catches in areas permitted for traditional Indonesian fishing.

New distribution records of the Vulnerable fossil shark Hemipristis elongata from eastern Indonesia call for improved fisheries management

Genetically verified catch data from fishers in eastern Indonesia provide new distribution records for the fossil shark Hemipristis elongata in the Halmahera, Seram and Arafura seas. Previously only recorded from the island of Java, this study reports a range extension for this species of >2000Â km across the Indonesian archipelago, suggesting that fossil sharks are subjected to fishing pressure over a much larger geographic area than implied by previous species records. We recommend a review of the current species assessment to reflect the reported range extension and inform management of this fishery-Targeted shark.