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Abstract  The biology of elasmobranchs makes them very vulnerable to fishing pressure and there is increasing international concern over their exploitation. In northern Australia the stocks of some species may be shared with those in southern Indonesia. Indonesia has the highest landings of elasmobranchs worldwide (>100,000 t p.a.) and millions of Indonesian artisanal fishers rely heavily on elasmobranchs taken in target fisheries. They are also taken by industrial trawlers and as bycatch in pelagic tuna fisheries. This paper, resulting from a collaborative project between Australia and Indonesia, summarises the elasmobranch fisheries; the characteristics of the fisheries are outlined, the status of the stocks are assessed, and management options described and discussed. The project focussed on representative markets and fish landing sites in southern Indonesia from 2001 to 2005. Data were from market surveys, the records of the Indonesian Directorate General of Capture Fisheries, and from research cruises. Data from the ongoing tuna monitoring programme showed that shark bycatch from the tuna fleets forms about 11% of shark landings in Indonesia. Yield per recruit and related analyses were used to integrate biological information to indicate the productivity of each species to allow for management policy options and constraints. Research cruise data show that catch rates of elasmobranchs in the Java Sea declined by at least one order of magnitude between 1976 and 1997. The results indicate strongly that many of the shark and ray species in Indonesia are overfished and that the most effective management strategy may need to involve capacity control, such as licencing, gear restrictions and catch limits, together with controls on the fin trade. [ABSTRACT FROM AUTHOR]

This paper used the case study of the Wakatobi Marine National Park, Indonesia to examine changes in the diversity, density and maturity of grouper species over a 5-year period following the establishment of a small-scale no-take area (NTA). This work was carried out to investigate whether “small” NTAs could be effective management strategies over a time scale that is relevant to local fishery communities and their perception of management success. Our research also documents the ecology of these species, information essential if we are to understand how management practises are to affect coral reef fish species. Designation of this “small NTA” increased the density of groupers by 30% over a 5-year period of protected status. After 5 years of protection, grouper populations within this NTA were more mature and double the density of those within the adjacent lightly fished sites and nearly five times those of a heavily fished site. During this time all other nearby fished sites underwent large declines in grouper density. The nearby lightly fished Kaledupa site decreased by up to 50% year−1. Such drastic declines are considered the impact of the exponential development of ever efficient and unsustainable methods of fishing within the study region. This NTA was not of benefit to all grouper species; the reasons for which are not clear. Such questions require further detailed research about the life history, population and behavioural ecology of Indo-Pacific grouper species. Such information is critical for urgently needed fisheries management. The present study found that a small scale NTA of 500 m length was large enough to increase the population of top predatory fish. In conjunction with other socially acceptable small scale NTAs it could help maintain and increase important fish stocks over a larger area. The use of “small” NTAs within networks of reserves should become a useful tool in the management of the locally exploited coral reefs. [ABSTRACT FROM AUTHOR]

The snakehead gudgeon, Giuris laglaizei, is a native species in the Philippines. Recently, this fish was also reported in Indonesia. This species is exploited for use as food and in some localities, even the fry are harvested in large numbers. In this study, the genetic diversity of six lacustrine populations of the species in the Philippines was examined based on the 852-bp full-length sequence of the mitochondrial DNA control region (mtDNA CR). A total of 107 haplotypes were recovered from 182 mtDNA CR sequences. High levels of nucleotide and haplotype diversities were found for the populations in Lake Mainit, Lake Taal, and Lake Naujan. The populations in Lake Lanao, Laguna de Bay, and Lake Paoay had high levels of haplotype diversity, but low levels of nucleotide diversity. The median-joining network showed geographic separation of the northern populations (Laguna de Bay, Taal, Naujan, and Paoay) from the southern populations (Lanao and Mainit). Pairwise FST value was lowest and non-significant (FST = 0.013; P = 0.149) between the populations from lakes Lanao and Mainit. This provides genetic support to previous claims that G. laglaizei in Lake Lanao came from Lake Mainit. On the other hand, significant genetic differentiation that ranged from moderate to very large (FST = 0.079–0.434) was detected among the northern populations. Despite the overall high levels of genetic diversity detected in this study, like any fishery resource, G. laglaizei still merits conservation and fishery management plans for sustainable harvest and to ensure the maintenance of high levels of genetic diversity. [ABSTRACT FROM AUTHOR]

Ocean warming has been affecting marine ecosystems over the past few decades. The signature of ocean warming in global fisheries catch data has been identified through a variety of methods, one of which is the mean temperature of the catch (MTC) index. The MTC is derived from the average temperature preference of fished species weighted by their contribution to annual catches. Here, we used MTC to explore the fisheries catch responses to warming, from 1950 to 2016, along a latitudinal gradient in the western Pacific Ocean, from 37° N, via 2.5° S in the central western Pacific, to 36° S. The tropicalization of catches in a given geographic space, i.e., the increased catch of species with affinity to warmer waters, as a result of increasing sea temperature and the associated poleward migration of species, rather than any large-scale oceanographic variability, was apparent through the increasing MTC at higher latitudes. In particular, MTC in temperate Japan increased by 0.33 °C per decade over the time series. The MTC in subtropical/temperate southeast Australia increased by 0.24 °C per decade over the full time period and by 1.24 °C per decade after 2002. The observed MTC increase was caused by the increasing dominance of thermophilous (preferring warmer waters) over psychrophilous (preferring cooler waters) taxa in the catches in these waters. On the other hand, the MTC in tropical Indonesian waters, as well as the ratio of thermophilous to psychrophilous taxa, showed a gentle yet consistent decrease of 0.05 °C per decade over the full time period. This finding supports the tropicalization hypothesis, given the limited scope for further tropicalization of catches in the already tropical ecosystem of Indonesia. Ocean warming has indeed been altering the distribution of marine organisms, particularly in temperate ecosystems as thermophilous taxa become more abundant, while psychrophilous taxa abundance decreases. Tropicalization impacts fisheries and catch composition and is, therefore, expected to cause conflicts among fishers and challenge fisheries management. [ABSTRACT FROM AUTHOR]

Trace metals are vital to primary productivity and play an essential role as main components in regulating oceanic biogeochemical cycles. Dissolved and particulate trace metals within the water column may vary due to primary production, temperature, and nutrient changes, factors that may also vary spatially and temporally. Furthermore, assessment of trace metals mainly relies on in situ observation, and so wide-area investigation of trace-metal concentration may be challenging and subject to technical constraints. A specific approach is therefore necessary that combines biogeochemical proxies, satellite data, and trace-metal linear correlation. This study aims to assess the potential spatio-temporal variability of sea surface cadmium (Cd) and copper (Cu) concentrations in Indonesian seas and surrounding areas. The correlations of Cd and Cu concentrations with primary production and nutrient data were used to convert hindcast satellite data into estimates of the metals' concentrations. The potential variability of trace metals can be determined by overlaying both data. Indonesia's Fisheries Management Areas (FMAs) were used for data clustering and analysis. The results show that Cd and Cu trace metals have similar distribution patterns throughout the year. However, dissolved Cu has a more diverse coverage area than dissolved Cd, including within the Halmahera, Seram, and Maluku Seas (FMAs 716 and 717), the Makassar Strait (FMA 717), and the Java–Sumatra upwelling area (FMA 573). Both Cd and Cu concentrations in the Java–Sumatra upwelling region follow the periodic upwelling pattern. Overall, both Cd and Cu show a declining trend in concentration from 2012 to 2019. It is estimated that dissolved Cd concentration declined from 1500–2000 pmol/kg in 2012 to 1000–1500 pmol/kg in 2019 for all locations. Dissolved Cu concentration decreased from 30–35 nmol/kg in 2012 to 25–30 nmol/kg in 2019. Estimated dissolved Cd and Cu follow the linear functions of silicate (SiO4), nitrate (NO3), and primary productivity. The fluctuation of anthropogenic activities and global warming are likely to indirectly impact the decline in metal concentrations by affecting nutrients and primary productivity. [ABSTRACT FROM AUTHOR]

Monitoring the use of anchored fish aggregating devices (AFADs) is essential for effective fisheries management. However, detecting the use of these devices is a significant challenge for fisheries management in Indonesia. These devices are continually deployed at large scales, due to large numbers of users and high failure rates, increasing the difficulty of monitoring AFADs. To address this challenge, tracking devices were attached to 34 handline fishing vessels in Indonesia over a month period each. Given there are an estimated 10,000–50,000 unlicensed AFADs in operation, Indonesian fishing grounds provided an ideal case study location to evaluate whether we could apply spatial modeling approaches to detect AFAD usage and fish catch success. We performed a spatial cluster analysis on tracking data to identify fishing grounds and determine whether AFADs were in use. Interviews with fishers were undertaken to validate these findings. We detected 139 possible AFADs, of which 72 were positively classified as AFADs. Our approach enabled us to estimate AFAD use and sharing by vessels, predict catches, and infer AFAD lifetimes. Key implications from our study include the potential to estimate AFAD densities and deployment rates, and thus compliance with Indonesia regulations, based on vessel tracking data. [ABSTRACT FROM AUTHOR]

We identify fishery management implications from a long-term monitoring program focusing on spawning aggregations of high valued reef fish in Komodo National Park (KNP), Eastern Indonesia. Management objectives of KNP are not only to protect biodiversity, but also to conserve spawning stocks of high-valued commercial species for the replenishment of surrounding fishing grounds. We monitored two sites twice monthly over five years for two species of grouper, Epinephelus fuscoguttatus and Plectropomus areolatus. One site had an aggregation of both E. fuscoguttatus and P. areolatus, whereas the other site contained an aggregation of P. areolatus only. Over the five years monitoring period, aggregations typically formed during each full moon between September and February. Additionally, P. areolatus occasionally aggregated during new moons between April and July. We observed spawning only once, but because formation of aggregations were correlated to a higher incidence of behavior and signs indicative of reproduction and because most fish present were adults, it is likely that the formation of aggregations was associated with spawning. Over the five years monitoring period there was a reduction in mean fish size of up to 8 cm for P. areolatus, and a reduction in numbers of aggregating E. fuscoguttatus. Despite limited protection initiated in 2001, both sites are still heavily fished by local artisanal fishers. Because the observed reductions in size and in numbers could be caused by fishing pressure, managers should follow the precautionary principle by putting additional protective management in place. Since both species are relatively long-lived, at least five years of continued monitoring may be necessary to determine the outcome of management intervention. The variability in timing of aggregation in respect to season and moon phase in P. areolatus indicates that long-term monitoring must cover the entire year and both moon phases. [ABSTRACT FROM AUTHOR]