A1 Refereed original research article in a scientific journal
Anadromous trout threatened by whitefish gill-net fisheries in the northern Baltic Sea
Authors: Kallio-Nyberg I, Veneranta L, Saloniemi I, Salminen M
Publisher: WILEY
Publication year: 2018
Journal: Journal of Applied Ichthyology
Journal name in source: JOURNAL OF APPLIED ICHTHYOLOGY
Journal acronym: J APPL ICHTHYOL
Volume: 34
Issue: 5
First page : 1145
Last page: 1152
Number of pages: 8
ISSN: 0175-8659
eISSN: 1439-0426
DOI: https://doi.org/10.1111/jai.13771
Abstract
We estimated the effect of the gill-net fisheries targeted at whitefish (Coregonus sp.) on anadromous sea trout, Salmo trutta, in the Gulf of Bothnia, Baltic Sea using separate data for fish species. The analysis of sea trout captures was based on tagging and recapture data collected in 1998-2011, while whitefish data were derived from individual samples of commercial fisheries from the same period. The mesh sizes used in gill-net fishing and the seasonal and temporal distributions of recaptured sea trout and sampled whitefish were compared in the northern and southern Gulf of Bothnia. The trout had typically spent 1-2years at sea, and they were mainly immature with a median body length of 40-43cm at the time of recapture in gill nets. Despite the increase in the minimum permitted landing size from 40 to 50cm in 2008, the median length of recaptured trout remained unchanged during the study period. Most (59%) of the gillnetted trout were caught in the southern Gulf of Bothnia in gill nets with mesh sizes of 40-45mm, which were also used in the whitefish fishery (72%). In the northern Gulf of Bothnia, nets with a smaller mesh size of 25-39mm took 83% of the whitefish catch and 39% from recaptured trout. In both areas, the overlap in mesh sizes used to gill-net catch whitefish and sea trout increased during the study period. There were clear seasonal and areal differences in the relative probability of sea trout being captured in gill nets, suggesting that carefully tailored spatial and temporal restrictions on gill-net fisheries could provide a tool to protect young sea trout without causing intolerable difficulties for the fisheries targeting other species.
We estimated the effect of the gill-net fisheries targeted at whitefish (Coregonus sp.) on anadromous sea trout, Salmo trutta, in the Gulf of Bothnia, Baltic Sea using separate data for fish species. The analysis of sea trout captures was based on tagging and recapture data collected in 1998-2011, while whitefish data were derived from individual samples of commercial fisheries from the same period. The mesh sizes used in gill-net fishing and the seasonal and temporal distributions of recaptured sea trout and sampled whitefish were compared in the northern and southern Gulf of Bothnia. The trout had typically spent 1-2years at sea, and they were mainly immature with a median body length of 40-43cm at the time of recapture in gill nets. Despite the increase in the minimum permitted landing size from 40 to 50cm in 2008, the median length of recaptured trout remained unchanged during the study period. Most (59%) of the gillnetted trout were caught in the southern Gulf of Bothnia in gill nets with mesh sizes of 40-45mm, which were also used in the whitefish fishery (72%). In the northern Gulf of Bothnia, nets with a smaller mesh size of 25-39mm took 83% of the whitefish catch and 39% from recaptured trout. In both areas, the overlap in mesh sizes used to gill-net catch whitefish and sea trout increased during the study period. There were clear seasonal and areal differences in the relative probability of sea trout being captured in gill nets, suggesting that carefully tailored spatial and temporal restrictions on gill-net fisheries could provide a tool to protect young sea trout without causing intolerable difficulties for the fisheries targeting other species.
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