Seabird Bycatch In Longline Fisheries Research Articles

PERKEMBANGAN PENGELOLAAN PERIKANAN GLOBAL

Global fisheries production has been marked by the fast growing pattern of capture fisheries production. During the last five decades marine fisheries production demonstrated an increase of nearly 500% or an annual average increase of 4.5%. this spectacular increase raised a global concern since it accompanied by overexploitation of resources in various parts of the world ocean. This concern has led to a series of negotiation in international arena that resulted in the formulation and finally adaption of the Code of Conduct for Responsible Fisheries in FAO in 1995. Elaboration of the implementation of the Code brought about the formulation of International Plan of Action (IPOA) burning issues of priority for which member countries of FAO are encouraged to translate it into National Plan of Action (NPOA). Four NPOA has been available including IPOA for sharks, for seabird bycatch in longline fisheries, for fishing capacity and for IUU fishing. Regional Fisheries Organization (RFO) in recent years has tasked to deal with management of living resources that do not respect administrative boundaries, such as some species of tuna and small pelages. Some of the fish resources exploited by the Indonesian fishers move across EEZ into high seas for which it falls within the responsibility of regional fisheries organization to manage. Indonesia is therefore encouraged to join such RFO to assure active participation in the management of the resources. Nonetheless, the administrative bureaucracy has hindred the process.

K-aggregated transformation of discrete distributions improves modeling count data with excess ones

The excess one pattern in count data has been documented in ecology but it has not been explicitly modeled or examined. In this study, we introduce a k-aggregated transformation of discrete distributions to better model count data with excess ones in a Bayesian generalized linear model framework and demonstrate its use with two groups of case studies (group 1: seabird bycatch in longline fisheries and Legionnaires disease incidence; group 2: survey abundance of Leadbeater’s possum and Frigatebird nesting sites). Group 1 examples have a clear excess one data pattern, and these examples are used to demonstrate the concept of the k-aggregation technique. On the other hand, group 2 examples lack a clear excess one pattern, and a modeler may not be motivated enough to use the k-aggregation technique in these cases. Nonetheless, k-aggregated transformation demonstrated better performance for both groups of examples. In all our case studies, the excess zero pattern co-occurred with an excess one pattern, and the excess zeros were modeled thorough either a zero-inflated or hurdle configuration. The better performance of k-aggregated distributions is due to their flexibility of adapting to the relatively high frequency of singletons in the data sets. This new technique has broad applicability and utility in improving modeling count data with potential excess ones.

Diving behaviour of Grey Petrels and its relevance for mitigating long-line by-catch

The Grey Petrel (Procellaria cinerea) is listed as Near Threatened globally owing to incidental mortality on long-line fishing gear and reduced breeding success on islands caused by the introduction of alien predators. However, there are few studies of its foraging ecology and none of its diving behaviour. We obtained data from temperature-depth recorders (n = 7 birds) and global positioning satellite trackers (n = 15) deployed on Grey Petrels breeding on Gough Island, South Atlantic Ocean. Most birds foraged in the productive oceanic waters west or north-west of South Georgia. Average maximum dive-depth was 3.2 ± 2.2 m with most dives <5 m (85%) and 95% of dives <7 m deep. The maximum dive-depth (22 m) was deeper than previous measurements of dive-depth in Procellaria petrels, and maximum dive-duration also was longer than previously recorded in Procellaria petrels (at least 39 s). Individuals varied greatly in the mean number of dives per day (range 0.4-24.5). Sex did not influence depth or duration of dives but sample sizes were small. The time of day influenced dive-depth, and dives during daylight were, on average, deeper than dives at night, but the effect was weak; the maximum dive-depth at night was 17 m. By providing insights into the diving behaviour of Grey Petrels our findings help to explain their high mortality on fishing long-lines. We suggest that fisheries adopt bird-scaring lines that protect long-lines from scavenging seabirds during the setting process to a depth of at least 10 m, which could be achieved by increasing line-weighting or modifying bird-scaring lines, or both. An understanding of the foraging ecology of commonly recorded by-catch species, such as Grey Petrels, is essential in the design of future devices to mitigate seabird by-catch in long-line fisheries.

Diving behaviour of white-chinned petrels and its relevance for mitigating longline bycatch

The white-chinned petrel (Procellaria aequinoctialis) is the seabird species most commonly killed by Southern Hemisphere longline fisheries. Despite the importance of diving ability for mitigating longline bycatch, little is known of this species’ diving behaviour. We obtained data from temperature–depth recorders from nine white-chinned petrels breeding on Marion Island, southwestern Indian Ocean, during the late incubation and chick-rearing period. Maximum dive depth (16 m) was slightly deeper than the previous estimate (13 m), but varied considerably among individuals (range 2–16 m). Males dived deeper than females, and birds feeding chicks dived deeper than incubating birds, but dive rate did not differ between the sexes. Time of day had no significant effect on dive depth or rate. Our findings will help to improve the design and performance of mitigation measures aimed at reducing seabird bycatch in longline fisheries, such as the calculation of minimum line sink rates and optimum aerial coverage of bird-scaring lines.

Managing Antarctic Marine Living Resources: The CCAMLR Approach

AbstractThis paper documents the experiences of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) in developing, and implementing, its fisheries conservation and management measures. Examples are given to show how the provisions of Article II of the Convention on the Conservation of Antarctic Marine Living Resources (CAMLR Convention) have been applied in practice. Generally, these provisions strive for an ecosystem-based and precautionary approach to the management of harvested and non-harvested species. Emphasis is given to the development of management measures to deal with: (a) uncertainty associated with new and exploratory fisheries, (b) reduction and elimination (i.e.minimisation) of seabird bycatch in longline fisheries, (c) trade-related measures to combat illegal, unreported and unregulated (IUU) fishing on CCAMLR species, and (d) general environmental protection. CCAMLR's achievements are evaluated, potential threats to its future effectiveness are identified and some possible counteractions are offered.

How fast do demersal longlines sink?

Longlines that sink fast reduce the time available to seabirds to attack baited hooks and are important in efforts to minimise seabird by-catch in longline fisheries. We measured sink rates in still seawater of longlines commonly used in the world’s demersal fisheries. Lines with integrated weight (lead cores) sank two to three times faster (45–52 cm/s) than conventional (unweighted) lines. Conventional 9 mm diameter lines made from polyester sank at 23 cm/s compared to 18 cm/s for 9 mm Silver lines (blend of polyester, polyethylene and polypropylene). Samples of lines set by hand in still water sank significantly faster than longlines set from a fishing vessel, presumably because of the effect of the sea swell and upwellings from the propeller on the line set from the vessel.

Seabird By-Catch in Small-Scale Longline Fisheries in Northern Peru

-Longlining has been encouraged in Peru as an opportunity for small-scale fishermen to reduce cetacean mortality in gill nets. Very little is known about seabird by-catch in this longline fishery. In January 1999, we conducted surveys in five fishing villages in northern Peru to estimate seabird by-catch and 29 fishermen were interviewed. Eighty percent of the fishermen used frozen bait, which increases the probability of seabird mortality. Ninety percent of fishermen confirmed that birds are hooked while setting the gear. Additionally, we found that over 40% of hooked seabirds were albatrosses. The most common albatross off northern Peru is the Waved Albatross (Phoebastria irrorata) and about 60% of the population of the Chatham Island Albatross (Thalassarche eremita) winters off Peru. Both species are considered threatened due to their small population sizes. Seabird by-catch in the Peruvian small-scale longline fishery should be of conservation concern; pooled estimates of by-catch rates based on interviews were 1 to 2 birds/1,000 hooks. The estimated by-catch of albatrosses by the entire fleet is likely to lie between 2,370 and 5,610 birds each year, which represents between 5% and 13% of the pooled populations of the Waved and Chatham Island Albatrosses. Even though these numbers are extrapolations, they can be considered a rough indicator of the magnitude of the seabird by-catch by the small-scale longline fishery in Peru. Further research that includes onboard seabird by-catch surveys as well as a larger sample of interviews with fishermen are required. Public awareness that encourages the implementation of by-catch deterrence measures such as bird lines, night setting of hooks, and the use of fresh bait, will help reduce by-catch and bait loss, thus benefiting fishermen and promoting albatross conservation. Received 10 July, accepted 28 September 2000.