12. Conservation of Marine Living Resources

This chapter argues that the conservation of marine living resources presents complex problems of regulation and management. The oceans represent the least understood ecosystem on this earth and this makes the conservation of marine life and resources, and the regulation of such, very difficult and complicated. The chapter gives an overview of the law as it stands. International law on conservation and sustainable use of marine living resources has developed very slowly thus far. Effective regimes for conservation of marine living resources have to address not only sustainable use of targeted stocks, but also incidental catch of other species, conservation of biological diversity, and protection of the marine ecosystems which provide the main habitat for fish stocks and other species. The chapter concludes that developing a legal regime that provides for sustainable use and conservation of the ocean’s living resources and biological diversity within the framework of the general law of the sea will continue to remain problematic.

Incidental catch of marine organisms registered in the Chilean Antarctic krill fishery, years 2012-2016

Krill (Euphausia superba) catch is currently the most relevant fishery industry in Antarctic waters. This resource is a keystone species in the Antarctic food web, sustaining the contribution to the trophic ecology of many invertebrate and vertebrate species. To catch krill, part of the fleet in this fishery uses large mid-water nets that also retain a diversity of other organisms like plankton, meroplankton, and fish species as bycatch. Therefore, it is necessary to understand and evaluate the magnitude of this incidental catch, as well as the potential interactions between krill fishing gear with seabirds and mammals. To estimate the composition and extent of bycatch for this fishery included 784 samples of 25 kg and an equal number of 1 kg sub-samples obtained from Antarctic krill catches in Subarea 48, between years 2012 and 2016. A total of 15 fish species were identified along with the record of five other taxa and other unidentified specimens. The most relevant fish species bycaught by weight were mackerel icefish Champsocephalus gunnari, South Georgia icefish Pseudochaenichthys georgianus, and painted notie Lepidonotothen larseni. Additionally, 20 interactions with seabirds and nine interactions with Antarctic fur seals (Arctocephalus gazella) were registered. In the five years of operations, only three seabirds died, and only two individuals of A. gazelle caught by the net were killed.

Reproductive ecology of the witch guitarfish Zapteryx xyster Jordan & Evermann, 1896 (Chondrichtyes: Trygonorrhinidae) in the Gulf of Tehuantepec, Mexican Pacific

From January 2008 to December 2009, 451 specimens of witch guitarfish Zapteryx xyster were caught in the Gulf of Tehuantepec. Total weight, total length (TL), sex, maturity stage and catch depth were recorded for each specimen. Maturity stage distribution exhibited significant differences with respect to depth. The data indicated that adults migrated towards shallow waters (25–37m) to reproduce, starting in February. Males reached maturity at 44cmTL, whereas females reached maturity at 48cmTL. Witch guitarfish females are synchronous; therefore, ovulation and mating begin in March and parturition begins in April. Females showed a 2-year cycle with consecutive vitellogenesis and gestation. Fecundity was five to eight embryos (mean six embryos) and the sex ratio of embryos was 1:1. Birth occurred in April and May, with an average size at parturition of 17.3cmTL. There was sexual dichromatism between males and females during the breeding period, and sexual polymorphism in adult females. The incidental catch of the witch guitarfish during courtship and mating threatens the survival of this species.

Genomics to aid species delimitation and effective conservation of the Sharpnose Guitarfish (Glaucostegus granulatus)

The Sharpnose Guitarfish (Glaucostegus granulatus) is one of fifteen critically endangered Rhino Rays which has been exploited as incidental catch, leading to severe population depletions and localized disappearances. Like many chondrichthyan species, there are no species-specific time-series data available for the Sharpnose Guitarfish that can be used to calculate population reduction, partly due to a lack of species-specific reporting as well as limitations in accurate taxonomic identification. We here present the first complete mitochondrial genome and partial nuclear genome of the species and the first detail phylogenetic assessment of the species. We expect that data presented in the current manuscript will aid in accurate species-specific landing and population assessments of the species in the future and will enable conservation efforts to protect and recover remaining populations.

Untangling the Indonesian tangle net fishery: describing a data-poor fishery targeting large threatened rays (Order Batoidea)

Shark-like batoids (Order Rhinopristiformes) are normally taken as incidental catch in fisheries targeting other species, one exception is a poorly understood Indonesian tangle net fishery. Market surveys of Muara Angke landing port recorded landed catch for this fishery. Recent catch data from Indonesian Capture Fisheries (2017 – 2018) were also examined to provide contemporary information. During the market surveys, 1,559 elasmobranchs were recorded, comprised of 24 species of batoids and nine species of sharks. The most abundant were pink whiprayPateobatis faiand bottlenose wedgefishRhynchobatus australiae, the latter being the main target species. Catch composition differed between individual tangle net boat landings, likely reflecting different fishing grounds, seasonal variation and potential localised declines in species over time. The fishery is highly selective for larger size classes, but smaller size classes of target species are also caught in high numbers in other Indonesian fisheries such as trawl, small mesh gillnet, and hand- and long-line fisheries. As of July 2018, the tangle net fishery was still operating, but few wedgefish were caught and the main landed catch was stingrays. Evidence of substantial and rapid declines in landings of wedgefish species, raises concerns about the status of shark-like batoids and stingrays in Indonesia.