Trap selectivity and the effects of altering gear design in the South African rock lobster Jasus lalandii commercial fishery

DS SCHOEMAN, AC Cockcroft, DL Van Zylt, PC Goosen

    Research output: Contribution to journalArticle

    7 Citations (Scopus)

    Abstract

    The current trap fishery for the West Coast rock lobster Jasus lalandii in South African waters results in the capture, sorting and release of large numbers of undersized animals. Once removed from the water, they are vulnerable to damage from numerous sources. Even sub-lethal injury may result in a considerable reduction to individual productivity through decreased growth or reproductive potential. Given that the J. lalandii resource is heavily depleted, such wastage may have severe repercussions for the sustainability of the fishery. In an attempt to reduce these losses, 20% of the fishing gear used by the rock lobster industry has been modified to include grids designed to allow undersized rock lobsters (mainly females) to escape the traps before they are hauled. The efficiency of this gear (and two alternatives) was assessed by comparison with standard commercial gear over a range of fishing grounds. Results indicated that, in comparison to standard commercial traps, none of the alternative trap designs would be beneficial to the fishery in the long term, provided that overnight sets remain the most common fishing method. SELECT models were used to evaluate the fishing properties of commercial and bottom-grid traps relative to those of control (fine-mesh) traps. The results indicated that, given the choice, a rock lobster would preferentially enter a commercial trap, followed by a control trap, with bottom-grid traps being the least attractive. This suggests some level of saturation of control traps, a possibility that is of particular concern because the control trap design is used in a fishery-independent monitoring survey.
    LanguageEnglish
    Pages37-48
    JournalSouth African Journal of Marine Science
    Volume24
    Publication statusPublished - 2002

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    fishery
    rock
    fishing
    reproductive potential
    fishing gear
    sorting
    sustainability
    saturation
    water
    productivity
    damage
    effect
    commercial fishery
    animal
    coast
    industry
    monitoring
    resource
    comparison

    Cite this

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    title = "Trap selectivity and the effects of altering gear design in the South African rock lobster Jasus lalandii commercial fishery",
    abstract = "The current trap fishery for the West Coast rock lobster Jasus lalandii in South African waters results in the capture, sorting and release of large numbers of undersized animals. Once removed from the water, they are vulnerable to damage from numerous sources. Even sub-lethal injury may result in a considerable reduction to individual productivity through decreased growth or reproductive potential. Given that the J. lalandii resource is heavily depleted, such wastage may have severe repercussions for the sustainability of the fishery. In an attempt to reduce these losses, 20{\%} of the fishing gear used by the rock lobster industry has been modified to include grids designed to allow undersized rock lobsters (mainly females) to escape the traps before they are hauled. The efficiency of this gear (and two alternatives) was assessed by comparison with standard commercial gear over a range of fishing grounds. Results indicated that, in comparison to standard commercial traps, none of the alternative trap designs would be beneficial to the fishery in the long term, provided that overnight sets remain the most common fishing method. SELECT models were used to evaluate the fishing properties of commercial and bottom-grid traps relative to those of control (fine-mesh) traps. The results indicated that, given the choice, a rock lobster would preferentially enter a commercial trap, followed by a control trap, with bottom-grid traps being the least attractive. This suggests some level of saturation of control traps, a possibility that is of particular concern because the control trap design is used in a fishery-independent monitoring survey.",
    author = "DS SCHOEMAN and AC Cockcroft and {Van Zylt}, DL and PC Goosen",
    year = "2002",
    language = "English",
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    Trap selectivity and the effects of altering gear design in the South African rock lobster Jasus lalandii commercial fishery. / SCHOEMAN, DS; Cockcroft, AC; Van Zylt, DL; Goosen, PC.

    In: South African Journal of Marine Science, Vol. 24, 2002, p. 37-48.

    Research output: Contribution to journalArticle

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    AU - Goosen, PC

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    AB - The current trap fishery for the West Coast rock lobster Jasus lalandii in South African waters results in the capture, sorting and release of large numbers of undersized animals. Once removed from the water, they are vulnerable to damage from numerous sources. Even sub-lethal injury may result in a considerable reduction to individual productivity through decreased growth or reproductive potential. Given that the J. lalandii resource is heavily depleted, such wastage may have severe repercussions for the sustainability of the fishery. In an attempt to reduce these losses, 20% of the fishing gear used by the rock lobster industry has been modified to include grids designed to allow undersized rock lobsters (mainly females) to escape the traps before they are hauled. The efficiency of this gear (and two alternatives) was assessed by comparison with standard commercial gear over a range of fishing grounds. Results indicated that, in comparison to standard commercial traps, none of the alternative trap designs would be beneficial to the fishery in the long term, provided that overnight sets remain the most common fishing method. SELECT models were used to evaluate the fishing properties of commercial and bottom-grid traps relative to those of control (fine-mesh) traps. The results indicated that, given the choice, a rock lobster would preferentially enter a commercial trap, followed by a control trap, with bottom-grid traps being the least attractive. This suggests some level of saturation of control traps, a possibility that is of particular concern because the control trap design is used in a fishery-independent monitoring survey.

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