Catch Efficiency of Groundgears in a Bottom Trawl Fishery: A Case Study of the Barents Sea Haddock

Abstract

The catch efficiency of two types of groundgear—a conventional rockhopper and a new type of groundgear called the semicircular spreading gear (SCSG)—was investigated through experimental fishing for Haddock Melanogrammus aeglefinus conducted in the Barents Sea. A retainer bag was attached behind the footrope of the trawl, and the number of fish that were overrun by the trawl was compared with the catch in the trawl cod end. The catch efficiency increased slightly for larger Haddock for both groundgears. The SCSG was found to have a significantly higher catch efficiency than the conventional rockhopper groundgear. The estimated improvement in catch efficiency varied between 4.5% and 12.3%, with an equivalent reduction in escape rate underneath the groundgear of more than 70%. The rockhopper groundgear can have a catch efficiency as low as 76%, corresponding with values reported in previous studies. Average catch efficiency for the rockhopper gear was significantly lower during the night in comparison with the daytime. No such difference was found with the SCSG. The SCSG is more efficient for catching Haddock, and it is lighter than the rockhopper groundgear. Both are important factors in reducing seabed impact and fuel consumption. When compared to results of a similar study on Atlantic Cod Gadus morhua, we found that in general, both groundgears had a greater catch efficiency for Haddock, which accords with differences in behavior between the two species.

Inferring fish behaviour at the trawl mouth from escape location

“…The behavioural difference between Atlantic cod and haddock has played a vital role in developing separator trawls to separate Atlantic cod from the catch of haddock ( Brinkhof et al, 2017 ; Krag et al, 2010 ; Larsen et al, 2018 ). Increasing spaces between the fishing line and the seabed can increase the escape of Atlantic cod under the trawl, therefore reducing bycatch of Atlantic cod from haddock-directed fisheries ( Krag et al, 2010 ).…”

“…Increasingly, quantitative techniques have been used to describe fish behaviour at the trawl mouth that lead fish either escaping under or entering the trawl ( Albert, Harbitz & Høines, 2003 ; Bayse, Pol & He, 2016 ; Underwood et al, 2015 ). Additionally, the use of underwater video in combination with the catch data has shown potential for quantifying fish behaviour while herding ( Godø, 1999 ; Weinberg & Munro, 1999 ; Larsen et al, 2018 ).…”

Impact of ground gear design on catch efficiency in demersal trawl fishery

“…In commercial trawl fisheries, the choice between different ground gears often depends on the seabed type (He, 2007;He and Winger, 2010;Fakıoğlu et al, 2022), target fish (Krag et al, 2010;Brinkhof et al, 2017;Larsen et al, 2018) and presence of marine debris on the seafloor (Eryaşar et al, 2014). Our fishing trials were conducted on soft, flat seabed allowing use of SL and DL ground gears without risking gear damages.…”

“…The most common method to estimate absolute ground gear catch efficiency is to use small auxiliary nets attached behind the fishing line to recapture fish escaping under the ground gear (Krag et al, 2010;Brinkhof et al, 2017;Larsen et al, 2018). This method was first introduced by Engås and Godø (1986;1989), but it involves several operational challenges such as variable gear performance, debris accumulation, loss of seabed contact and requires short towing time (Dahm and Wienbeck, 1992;Dahm, 1997).…”

A tool to estimate the contribution of fishing gear modifications to reduce benthic impact

“…We demonstrate that in certain situations, gear modification can provide significant improvements in RBS, assuming gear catch efficiency is maintained. We are not able to account for potential changes in gear catch efficiency (Larsen et al., 2018; Poos et al., 2020) and not all modifications are feasible but have been included for completeness. Future developments of the tool should consider changes in gear catch efficiency based on modifications.…”