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Developing a full-scale shaking codend to reduce the capture of small fish.
Vang Y Nguyen1, Shannon M Bayse1, Zhaohai Cheng1
1Fisheries and Marine Institute, Memorial University of Newfoundland, St. John's, NL, Canada.
Plos One
|January 23, 2023
Summary
A novel shaking codend effectively reduces undersized redfish capture in trawls. This innovative design enhances fish escape, offering a promising solution for sustainable fisheries management.
Area of Science:
- Fisheries Science
- Marine Biology
- Engineering
Background:
- Undersized fish retention in redfish trawls poses ecological and economic challenges.
- Current codend designs struggle to effectively release small fish, leading to bycatch issues.
Purpose of the Study:
- To develop and evaluate a full-scale shaking codend to reduce the retention of undersized redfish (Sebastes spp.).
- To assess the movement and fishing characteristics of the shaking codend compared to a standard T90 codend.
Main Methods:
- A mechanical stimulating device was integrated into a T90 codend to create a 'shaking motion'.
- Flume tank tests evaluated codend dynamics (amplitude, acceleration, drag) at various velocities (1.0-1.8 kt).
- Field experiments were conducted to assess the impact on redfish capture, with preliminary results analyzed.
Main Results:
- The shaking codend exhibited significantly higher amplitude, acceleration, and drag forces than the standard T90 codend.
- Field tests indicated a significant reduction in the capture of small redfish (< 21 cm) using the shaking codend.
- The model for the shaking codend did not require contact probability, unlike the standard codend.
Conclusions:
- The shaking codend's unique dynamics effectively stimulate fish movement and increase escape probability.
- This technology presents a potentially effective method for reducing undersized redfish bycatch in trawl fisheries.
- The concept may be applicable to other trawl fisheries for minimizing the catch of small fish.
