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Using a double codend to reduce discard mortality
Broadhurst, M.K.; Millar, R.B.; Uhlmann, S.S. (2009). Using a double codend to reduce discard mortality. ICES J. Mar. Sci./J. Cons. int. Explor. Mer 66(10): 2077-2081.
In: ICES Journal of Marine Science. Academic Press: London. ISSN 1054-3139; e-ISSN 1095-9289, more
Peer reviewed article  

Available in  Authors 

    Catching methods > Net fishing > Trawling
    Metapenaeus macleayi (Haswell, 1879) [WoRMS]
Author keywords
    bycatch; discard mortality; unaccounted fishing mortality

Authors  Top 
  • Broadhurst, M.K.
  • Millar, R.B.
  • Uhlmann, S.S., more

    Traditional technical strategies for mitigating collateral fishing mortality have involved improving gear selectivity (to reduce bycatch) and, more recently, concomitant changes to onboard handling procedures to reduce some of the negative impacts to the remaining discards. A less common approach is to modify gears physically to minimize deleterious catching mechanisms and subsequent mortalities during fishing. This study aimed to investigate the utility of the latter category of modifications for penaeid trawls by separating a codend into two compartments (termed a double codend) to alleviate interactions between catches. Compared with a conventional design, the double codend significantly reduced the immediate (from 17.1 to 13.8%) and short-term (22.5 to 17.1%) mortalities of discarded juvenile school prawns (Metapenaeus macleayi). The effectiveness of the double codend remained independent of other factors known to affect the fate of discarded juvenile M. macleayi, including cloud cover and, owing to minimal variability, the weight of the total catch. However, irrespective of the codend configuration, overall mortalities were also positively correlated with the quantity of jellyfish. We conclude that when combined with modifications to improve selectivity and appropriate onboard handling strategies, compartmentalizing codend catches could cumulatively reduce unaccounted fishing mortality.

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