University of Helsinki.<\/a> \u201cGlobally, 18 million tonnes of wild fish such as capelin are harvested annually for domestic animal feed, so there is still work to do to further reduce the effects of aquaculture on wild fish populations.\u201d<\/p>\nLinking environmental and human influences with evolutionary changes<\/h3>\n \u201cOur earlier research had shown that the age at which salmon were maturing in this river was getting younger, and consequently the size of salmon that are spawning was also getting smaller, illustrating \u2018evolution in action\u2019. Important for demonstrating rapid evolution, there were also changes in their DNA at a gene known to be linked with maturation size and age,\u201d added Primmer.<\/p>\n
Dr\u00a0Yann Czorlich, the first author of the study, commented: \u201cThis previous research could not tell us what environmental or human influences might be linked with the evolutionary changes. To understand this, we needed to link the yearly changes in the salmon DNA variation with annual changes in environmental and human-linked factors.\u201d<\/p>\n
\u201cWe gathered literally millions of data-points about factors, including yearly water temperature, salmon fishing effort, and commercial fisheries catches of the fish salmon eat in the ocean, and compared them with our data on DNA changes in our 40-year time series.\u201d<\/p>\n
Changes in salmon fishing affect the size of wild salmon<\/h3>\n In addition to the indirect effect of capelin harvesting, the research team also identified a direct effect of salmon fishing in the river. \u201cWe found that a special net type, a salmon weir, that accounts for majority of net catches, is capturing predominantly smaller fish, although net fishing is often assumed to catch larger fish,\u201d said\u00a0Jaakko Erkinaro, a Research Professor at Natural Resources Institute Finland.<\/p>\n
The researchers analysed local indigenous knowledge to discover an answer for this surprising result: \u201cWe discussed with local S\u00e1mi fishers who have fished with salmon weir for decades, and they explained that, compared to other net types, salmon weir has smaller mesh size, is used later in the season and mostly in shallower waters, which increases the catch of smaller salmon. This likely explains the result,\u201d Erkinaro continued.<\/p>\n
Weir fishing has decreased in recent years, and simultaneously, the proportion of small, early maturing fish in spawning populations has increased. \u201cOur finding that there are different forms of fishing acting in opposite directions at different phases of their life-cycle highlights new challenges for salmon management, but also the value of having unique long-term data series at our disposal,\u201d noted Erkinaro.<\/p>\n
A unique long-term scale salmon archive<\/h3>\n The research team examined scale samples from salmon over a 40-year period and linked the variation of a gene that determines salmon reproduction age and size, with the effects of different fishing methods. The scale samples used for the study came from a unique long-term scale archive maintained by Luke.<\/p>\n
The archive holds samples from more than 150,000 salmon individuals collected by trained, volunteer fishers since the 1970\u2019s from River Teno, one of the most prolific salmon rivers in Europe. The scales were used to determine the age structure of the salmon population. They were also the source of DNA for genetic analysis.<\/p>\n
The study was conducted in co-operation between the University of Helsinki, the Natural Resources Institute Finland (Luke), the University of Turku and the Norwegian Institute for Nature Research (NINA). Funding for this study was received from the Academy of Finland and the European Research Council.<\/p>\n","protected":false},"excerpt":{"rendered":"
Researchers from Finland used genetic methods to determine if a fishery for an aquaculture fish food source, combined with changes in salmon fishing, are causing wild salmon sizes to reduce. The study, published recently in journal\u00a0Science, revealed that the shrinking size of the Atlantic salmon in the River Teno in Northern Finland might not be […]<\/p>\n","protected":false},"author":19,"featured_media":18978,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[24433,785],"tags":[700,3475,24180],"acf":[],"yoast_head":"\n
Wild salmon are getting smaller due to aquaculture<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n \n \n\t \n\t \n\t \n