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Improving species and size selectivity in the Baltic cod trawl fishery with two simple codend designs
Fisheries Research ( IF 2.4 ) Pub Date : 2021-01-02 , DOI: 10.1016/j.fishres.2020.105846
Niels Madsen , Ólafur A. Ingólfsson , Hans Nilsson , Petri Suuronen

The eastern Baltic cod (Gadus morhua) stock is at a critically low level and recruitment of the western Baltic cod stock is at the lowest observed level in over 30 years. The EU (European Union) landing obligation was introduced in 2015 for cod and in 2017 for plaice (Pleuronectes platessa). Size selective codend designs have been used in the Baltic cod trawl fishery for 25 years; however, there are still relatively high discard rates for cod, plaice and European flounder (Platichthys flesus; henceforth flounder) in the trawl fishery and landings of individuals below the minimum conservation reference size (MCRS). These problems call for additional improvements of species and size selectivity in the cod trawl fishery. In this study, two trawl codend designs were developed and tested to improve species and size selectivity in the Baltic cod trawl fishery. The codends were tested onboard a commercial trawler and the test codends were compared to the conventional Bacoma codend, which was fished simultaneously in a twin trawl rig. New codend designs were based on the Bacoma design, where the first test codend had a bottom net panel made of larger diamond meshes (nominal 130 mm mesh size) to improve selectivity in a cod fishery with high catch rates of flatfish. This codend showed a reduction of plaice and flounder, and cod below 45 cm, in the catches. The other test codend was a full square mesh codend (nominal 120 mm mesh size) developed for a cod directed fishery with low flatfish catches, and showed a marked reduction in the catch of cod below 50 cm, with no differences for flounder and plaice catches. With cod stocks at critically low levels and relatively high discard rates of cod, plaice and flounder, the simple codend designs tested in this study could benefit the sustainability of the Baltic cod trawl fishery, but with some loss of commercially targeted sizes.



中文翻译:

通过两种简单的编码物设计提高波罗的海鳕鱼拖网渔业的种类和大小选择性

东部波罗的海鳕鱼(大西洋鳕鳕)的股票是在一个非常低的水平和招聘的西方波罗的海鳕鱼种群正处于30多年来的最低观测水平。2015年对鳕鱼和2017鱼(Pleuronectes platesa)引入了欧盟(European Union)着陆义务。在波罗的海鳕鱼拖网渔业中使用尺寸选择性的code设计已有25年之久。但是,鳕鱼,和欧洲比目鱼的丢弃率仍然相对较高(Platiththys flesus;低于最低保护参考尺寸(MCRS)的拖网捕捞和上岸的比目鱼)。这些问题要求在鳕鱼拖网渔业中进一步改善种类和尺寸选择性。在这项研究中,开发了两个拖网设计并进行了测试,以提高波罗的海鳕鱼拖网渔业的种类和大小选择性。在商用拖网渔船上测试了这些编码鱼,并将这些编码鱼与传统的Bacoma编码鱼进行了比较,后者是在双拖网渔具中同时捕捞的。新的编码鱼的设计基于Bacoma设计,其中第一个测试编码鱼的底网面板由较大的菱形网眼(标称130毫米网眼大小)制成,以提高鳕鱼捕捞率较高的比目鱼的选择性。这个code鱼显示出pla和比目鱼的减少,鳕鱼在45厘米以下,在渔获物中。另一个测试code是为鳕鱼定向捕捞的低比目鱼捕捞量开发的全方形网眼code(标称尺寸为120毫米网目),并显示鳕鱼的捕捞量明显减少(低于50厘米),比目鱼和捕捞量没有差异。由于鳕鱼种群处于极低的水平,并且鳕鱼,和比目鱼的丢弃率较高,因此,本研究中测试的简单code鱼设计可有益于波罗的海鳕鱼拖网渔业的可持续性,但会损失一些商业目标规模。

更新日期:2021-01-04
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