Thumbnail Image

Differences in large-scale movement between free swimming and fish aggregating device (FAD) caught tuna

Year of publication 2013

Product type Meeting

Category Meeting document

Edition 1

Statutory body / Meeting title Indian Ocean Tuna Commission (IOTC)

Meeting symbol IOTC-2010-WPTT-06

Meeting Session Number 12

Language English

Also available in:
No results found.

Related items

Showing items related by metadata.

  • Thumbnail Image
  • Thumbnail Image
    Meeting
    Meeting document
  • Thumbnail Image
    Document
    Other document
    Movement behaviour of skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tuna at anchored fish aggregating devices (FADs) in the Maldives investigated using acoustic telemetry 2013
    Also available in:
    No results found.
    The pole and line tu fishery in the Maldives relies heavily on an array of 45 anchored fish aggregat- ing devices (FADs), making it one of the largest anchored FAD-based tu fisheries in the world. We examined the behaviour of skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tu around anchored FADs (1 000 to 2 000 m deep) in the Maldives using passive acoustic telemetry. Eight neighbouring FADs (distance range: 30 to 95 km, average: 50 km) were equipped with automated acoustic rece ivers in January 2009, for a period of 13 months. A total of 40 skipjack (37−54 cm FL) and 21 yellowfin (35−53 cm FL) tu were tagged with Vemco V13 transmitters in January (start of the northeast monsoon, dry season) and November (end of the southwest monsoon, wet season) 2009 and released at the two central FADs within this instrumented array. No movement between FADs was observed for any acoustically-tagged tu in the instrumented FAD array. These results suggest that FADs in the Maldives may a ct inde- pendently. The maximum time a tagged skipjack remained associated with a FAD was 12.8 days in January but only one day in November. In addition, residence times at FADs were found to differ with time (month) and space (FAD location) for skipjack tu, suggesting that exterl biotic factors (e.g., prey, conspecifics or predators) might influence the time this species spends at FADs. In November, the residence times of yellowfin tu (maximum observed time: 2.8 days) were three times greater t han those of skipjack tu at the same FADs. This specific difference could be explained either by the two species responding to different factors or by the species’ responses being dependent on the same factor but with different thresholds. No particular preference for time of departure from the FADs was observed. Some monospe- cific and multispecific pairs of acoustically-tagged individuals were observed leaving the FADs simultaneously. Thus, this study indicates a high degree of complexity in t he behavioural processes driving FAD associations.
Show more

Users also downloaded

Showing related downloaded files

  • Thumbnail Image
    Document
    Other document
    Global seaweeds and microalgae production 2021
    Also available in:
    No results found.
  • Thumbnail Image
    Booklet
    Corporate general interest
    Emissions due to agriculture
    Global, regional and country trends 2000–2018
    2021
    Also available in:
    No results found.
    The FAOSTAT emissions database is composed of several data domains covering the categories of the IPCC Agriculture, Forestry and Other Land Use (AFOLU) sector of the national GHG inventory. Energy use in agriculture is additionally included as relevant to emissions from agriculture as an economic production sector under the ISIC A statistical classification, though recognizing that, in terms of IPCC, they are instead part of the Energy sector of the national GHG inventory. FAO emissions estimates are available over the period 1961–2018 for agriculture production processes from crop and livestock activities. Land use emissions and removals are generally available only for the period 1990–2019. This analytical brief focuses on overall trends over the period 2000–2018.
  • Thumbnail Image
    Book (series)
    Technical study
    Assessment and management of biotoxin risks in bivalve molluscs 2011
    Also available in:
    No results found.
    Biotoxins produced by certain algal species can be accumulated by bivalve molluscs. This constitutes one of the major public health risks that need to be managed during shellfish production. With a view to aiding risk assessment, monitoring and surveillance programmes, this paper provides a range of information about the various biotoxins globally recorded in shellfish: levels detected, toxicological data, methods of analysis for detection and quantification of toxins, and the risk assessment ap proach for public health management. The complex chemical nature of the toxins, along with several analogues, hampers the development and validation of methods for their detection, for the evaluation of their toxicity and for the development of limits for shellfish safety management. This paper also illustrates the approach taken by the Codex Alimentarius Commission in developing guidelines for bivalve shellfish safety management and for establishing Codex standards for live and raw bivalve moll uscs.
Show more