{"id":2895,"date":"2020-05-05T07:00:25","date_gmt":"2020-05-05T07:00:25","guid":{"rendered":"http:\/\/habitat.fisheries.org\/?p=2895"},"modified":"2020-05-05T07:00:25","modified_gmt":"2020-05-05T07:00:25","slug":"how-lake-trout-use-ocean-habitat","status":"publish","type":"post","link":"https:\/\/units.fisheries.org\/habitat\/how-lake-trout-use-ocean-habitat\/","title":{"rendered":"How Lake Trout Use Ocean Habitat"},"content":{"rendered":"\n

Fishes like shad and salmon are well known for large annual migrations between rivers and oceans.\u00a0 This life history trait, known as anadromy, allows fish to take advantage of the perks of both habitats.\u00a0 Rivers and streams offer refuge from predators, whereas the ocean offers an abundance of food.\u00a0 Anadromy can also be found on a smaller scale, as is seen in the northern chars belonging to the genus Salvelinus<\/em>.\u00a0 These populations often include some individuals that migrate to sea and some that don\u2019t. Having these multiple strategies within a population increases the chances that some fish will survive sudden changes in environmental conditions.\u00a0 In northern areas where the growing season is short, freshwater habitat is not as productive as marine habitat (Gross et al. 1988).\u00a0 Here, anadromous fish migrate to the ocean to take advantage of the food available in this habitat.\u00a0 <\/p>\n\n\n\n

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Maude S\u00e9vigny of Universit\u00e9 Laval releases a giant lake trout. Photo by B. Malley.<\/figcaption><\/figure><\/div>\n\n\n\n

For a long time, scientists thought that one species of northern char, the lake trout (Salvelinus namaycush<\/em>), did not move between freshwater and marine habitats.\u00a0 Lake trout generally have a difficult time maintaining the balance between water and salt within their bodies when placed in saltwater (Hiroi and McCormick 2007), but there have been cases where this species was seen in the ocean (e.g., Swanson et al. 2010).\u00a0 This led to the question of whether lake trout were straying into the ocean occasionally or if some individuals used marine habitat as part of an annual migration.\u00a0 To address this, Les Harris (Fisheries and Oceans Canada) and colleagues conducted a two-part study that took place in the central Arctic region of Canada (Harris et al. 2020). First, these scientists collected otoliths (or ear bones) from 10 lake trout caught in four different rivers.\u00a0 As fish age, new layers are added to otoliths like the rings of a tree.\u00a0 Otoliths store elements like strontium at the same concentration as what is seen in the local environment, and can be used to determine if a fish has moved between marine and freshwater habitat throughout its lifetime because seawater has a higher concentration of strontium than freshwater. By measuring strontium in the lake trout otoliths, the scientists found that adult fish first migrated to the ocean at different ages (16-45 years) and there was a wide range in how often they used marine habitat throughout their lifetimes.\u00a0 Some of the fish only migrated to the ocean once, others up to nine times.\u00a0 <\/p>\n\n\n\n

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Les Harris surgically implants acoustic transmitter into an anadromous lake trout. Photo by JS Moore.<\/figcaption><\/figure><\/div>\n\n\n\n

Next, Harris and colleagues caught 5\nfish at the mouth of the Ekalluk River (in Canada\u2019s Nunavut territory) and\ntagged them with acoustic tags.  Fish were\ntracked as they moved between freshwater and marine habitats, and the\nscientists were able to develop a more detailed picture of the marine habitat\nlake trout prefer.  Tagged lake trout\nspent most of their time in estuaries and preferred to occupy the top layer of\nwater which was fresher and warmer rather than moving further and deeper into\nthe ocean.  Occasionally, individuals\nwould dive to deeper waters or move a little further out to sea, but these were\nshort trips after which fish returned to their preferred estuarine and\nsurface-water habitat.  This is in stark\ncontrast to their usual habits in lakes of occupying deep, cold water.   <\/p>\n\n\n\n

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Lake trout swims off after surgical implantation of an acoustic transmitter. Photo by B. Malley.<\/figcaption><\/figure><\/div>\n\n\n\n

Results from both parts of the study indicated that some lake trout do migrate between freshwater and estuaries for multiple years throughout their lifetime, but there is a wide range among individuals in how many times this occurs.\u00a0 In addition, the lake trout in this study seemed to prefer warmer habitat that had lower salinity, which follows that this species is not as adept at maintaining its salt and water balance as well as other salmonids.\u00a0 Harris and colleagues concluded that individuals within populations of lake trout in Canada\u2019s central Arctic have adapted to take advantage of productive estuary habitat.\u00a0 Utilizing marine habitat allows fish to grow at a faster rate and to a larger size, which can lead to a reproductive advantage (McDowall 2001).\u00a0 Unfortunately, this comes at the cost of greater energy use during migration and the danger of dying at sea.\u00a0 Such a tradeoff could explain why not all individuals within a lake trout population are anadromous. This study is the first to explore how populations of lake trout use marine habitat, and hopefully the anadromous strategy used by this species will continue to be studied.<\/p>\n\n\n\n

References:<\/strong><\/p>\n\n\n\n

Gross MR, Coleman RM, and McDowall RM.\n1988. Aquatic productivity and the evolution of diadromous fish migration. Science<\/em>. 239: 1291-1293.<\/p>\n\n\n\n

Hiroi J and McCormick SD. 2007.\nVariation in salinity tolerance, gill Na+\/K+-ATPase, Na+\/K+\/2Cl- cotransporter\nand mitochondria-rich cell distribution in three salmonids Salvelinus namaycush<\/em>, Salvelinus\nfontinalis<\/em> and Salmo salar<\/em>. Journal of Experimental Biology<\/em>. 210:\n1015-1024.<\/p>\n\n\n\n

Swanson HK, Kidd KA, Babaluk JA,\nWastle RJ, Yang PP, Halden NM, and Reist JD. 2010. Anadromy in Arctic\npopulation sof lake trout (Salvelinus\nnamaycush<\/em>): Otolith microchemistry, stable isotopes, and comparisons with\nArctic char (Salvelinus alpinus<\/em>).\nCanadian Journal of Fisheries and Aquatic Sciences. 67: 842-853.<\/p>\n\n\n\n

Harris LN, Swanson HK, Gilbert MJH,\nMalley BK, Fisk AT, and Moore JS. 2020. Anadromy and marine habitat use of Lake\ntrout (Salvelinus namaycush<\/em>) from the\ncentral Canadian Arctic. Journal of Fish\nBiology<\/em>. Early view. https:\/\/doi.org\/10.1111\/jfb.14305<\/p>\n\n\n\n

McDowall RM. 2001.  Anadromy and homing: two life-history traits\nwith adaptive synergies in salmonid fishes? Fish\nand Fisheries<\/em>. 2: 78-85.  <\/p>\n\n\n\n

Photo credits:<\/strong> B. Malley and JS Moore.<\/p>\n","protected":false},"excerpt":{"rendered":"

Fishes like shad and salmon are well known for large annual migrations between rivers and oceans.\u00a0 This life history trait, known as anadromy, allows fish to take advantage of the […]<\/p>\n","protected":false},"author":2,"featured_media":2898,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[76],"tags":[],"class_list":["post-2895","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research-brief"],"acf":[],"_links":{"self":[{"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/posts\/2895","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/comments?post=2895"}],"version-history":[{"count":0,"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/posts\/2895\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/"}],"wp:attachment":[{"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/media?parent=2895"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/categories?post=2895"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/units.fisheries.org\/habitat\/wp-json\/wp\/v2\/tags?post=2895"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}