Study

Assessment of an environmentally friendly, semi-pelagic fish trawl

  • Published source details Brewer D., Eayrs S., Mounsey R. & Wang Y. (1996) Assessment of an environmentally friendly, semi-pelagic fish trawl. Fisheries Research, 26, 225-237.

Actions

This study is summarised as evidence for the following.

Action Category

Modify a bottom trawl to raise parts of the gear off the seabed during fishing

Action Link
Marine Fish Conservation
  1. Modify a bottom trawl to raise parts of the gear off the seabed during fishing

    A replicated, randomized, controlled study in 1993 in two areas of seabed in the Gulf of Carpentaria, Australia (Brewer et al. 1996) found that unwanted catch of sharks Carcharinidae, other sharks/rays Elasmobranchii and non-commercial fish species was lower in bottom trawls rigged to fish above the seabed (no groundrope), compared to a conventional trawl with the groundrope in contact with the seabed. Overall, catch rates of unwanted sharks were lower for both raised trawl configurations, 0.4–0.5 m above the seabed (3 kg/h) and 0.8–0.9 m above the seabed (1 kg/h) compared to the conventional trawl (5 kg/h). No other sharks/rays were caught in either modified trawl, but 58 kg/h were caught in the conventional trawl. Catch of unwanted fish species was also lower with the trawl 0.4–0.5 m above the seabed (62 kg/h) and at 0.8–0.9 m above the seabed (12 kg/h) than in the conventional trawl (190 kg/h). In addition, catch rates were similar between both modified trawls and the conventional trawl for all 12 target or commercially valuable species caught (see original paper for data). In November 1993, two 18 × 18 km sites were trawled at 41–58 m depths with three trawl designs with 50 mm mesh codends: two trawls with the groundrope removed, and rigged to fish at either 0.4–0.5 m or 0.8–0.9 m above the seabed by means of floats on the headline floats and weights on the footrope, and one conventional trawl with a 170 kg footrope (see original paper for gear configurations). Sites were trawled alternately for three days at a time (five trawls a day, in separate grids) using a different gear each day, with the gear type randomly re-ordered each time. All catch species were identified and weighed.

    (Summarised by: Leo Clarke)

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