{"id":4449,"date":"2023-11-10T11:30:46","date_gmt":"2023-11-10T19:30:46","guid":{"rendered":"https:\/\/calsport.org\/fisheriesblog\/?p=4449"},"modified":"2023-11-10T11:30:46","modified_gmt":"2023-11-10T19:30:46","slug":"trucking-central-valley-salmon-smolts-from-hatcheries-to-salt-water","status":"publish","type":"post","link":"https:\/\/calsport.org\/fisheriesblog\/?p=4449","title":{"rendered":"Trucking Central Valley Salmon Smolts from Hatcheries to Salt Water"},"content":{"rendered":"

A November 1, 2023 article<\/a>, originally published in High Country News and later posted in Maven\u2019s Notebook, describes the practice of trucking juvenile salmon from hatcheries for release in salt water as a \u201cculprit,<\/em>\u201d stating:\u00a0<\/em><\/p>\n

According to a growing body of scientific evidence, it\u2019s also the reason that many salmon are getting lost on their way back to their birth rivers, placing the future resilience of the species at risk\u2026. These trucked hatchery fish may survive longer in the short term, but they will return to the river system years later with massive gaps in their memory and little sense of how to locate their spawning grounds. Instead, many end up wandering up unfamiliar rivers or streams and spawning far from home.<\/p><\/blockquote>\n

What the article doesn\u2019t say is that juvenile salmon released directly in San Francisco Bay or San Pablo Bay, or in the ocean, are as much as ten to a hundred times more likely to live to spawn as are juvenile fish released near their hatcheries of origin.<\/p>\n

It is true that trucked hatchery salmon smolts have a higher \u201cstraying\u201d rate than smolts that are released near the hatcheries in which they were raised.\u00a0 Sometimes, that difference in straying is quite dramatic.<\/p>\n

On the other hand, while straying does cause salmon to wander into Central Valley rivers other than those from which they came, most of the rivers to which they stray would have few if any salmon at all if it were not for these strays. \u00a0And right now, trucking is necessary for the water projects to meet their mitigation goals of putting salmon back into the ocean to sustain salmon fisheries.<\/p>\n

Furthermore, if it were not for trucking, the investment of hundreds of millions of dollars in salmon hatcheries would largely be for naught.\u00a0 Only in wetter years do releases of hatchery-raised salmon near the hatcheries come anywhere close to achieving hatchery production goals.\u00a0 In the drier years, when hatcheries provide their greatest benefit, very few fish released at or near the hatcheries survive downstream migration through Central Valley rivers and the Bay-Delta.<\/p>\n

Trucking also reduces the competition between hatchery smolts and wild fish for limited habitat downstream of the Valley\u2019s rim dams.<\/p>\n

Below, I provide examples of straying rates for the Mokelumne Hatchery and Coleman Hatchery, from which some of the highest percentages of straying occurs.\u00a0 The American and Feather River hatchery releases also have elevated straying of trucked smolts, but at much lower rates.<\/p>\n

Mokelumne River Hatchery Straying<\/strong><\/p>\n

One of the greatest straying problems is from the Mokelumne Hatchery smolt releases, especially in drought years.\u00a0 The Mokelumne Hatchery trucks more smolts percentage-wise than the other six salmon hatcheries.\u00a0 However, coastal releases of Mokelumne Hatchery fish in drought years 2014 and 2015 yielded returns of 0.79-1.15% compared to 0.01% from the river release below the hatchery (Table 1).<\/p>\n

However, straying rates for coast releases were greater than 50% to other rivers and hatcheries compared to 0% for the Mokelumne River releases (Figures 1-4).<\/p>\n

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Table 1.\u00a0 Mokelumne Hatchery selected release groups \u2013 number and survival rates<\/p><\/div>\n

\u00a0<\/strong>Coleman (Battle Creek) Hatchery Straying<\/strong><\/p>\n

Coleman Hatchery smolts trucked to the Bay have a much greater rate of straying than smolts released near the hatchery near the mouth of Battle Creek near Redding (Figures 5 and 6).\u00a0 However, smolts released near the hatchery have a much lower survival\/return rate (Table 2).<\/p>\n

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Table 2.\u00a0 Coleman Hatchery selected release groups \u2013 number and survival rates.<\/p><\/div>\n

Stray Counting<\/strong><\/p>\n

Other than showing up in these figures, strays are not accounted for in escapement estimates for individual rivers, and they are not counted in return tabulations of their hatchery of origin.\u00a0 Fish counted at a hatchery or in river surveys simply get accounted for in the escapement estimate for the river to which they return.\u00a0 As an example, tabulations for returns to the American River (Figure 7) show that in 2015, about a quarter of the tabulated escapement originally came as strays from the Mokelumne Hatchery.<\/p>\n

Conclusion<\/strong><\/p>\n

It is good practice to reduce straying of hatchery salmon.\u00a0 But in my view, arguments about straying often tend to obscure, not improve, the problems of poor survival of both wild and hatchery salmon in dry years due to inadequate flow and other aspects of poor water management.\u00a0 And as long as commercial and sport salmon fisheries in California and Oregon are substantially dependent on hatchery production in the Central Valley, it makes a lot of sense to prioritize the survival to adulthood of hatchery salmon over their fidelity to natal rivers and streams.<\/p>\n

For more on the trucking of juvenile hatchery production, see: https:\/\/calsport.org\/fisheriesblog\/?s=trucking&submit=Search<\/a><\/p>\n

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Figure 1. Returns from a Mokelumne Hatchery release to Golden Gate in 2014. Yellow dot is hatchery location. Green dot is release location.<\/p><\/div>\n

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Figure 2. Returns from Mokelumne Hatchery release to Santa Cruz Harbor in 2014.<\/p><\/div>\n

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Figure 3. Returns from Mokelumne Hatchery release to Moss Landing in Monterey Bay in 2015.<\/p><\/div>\n

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Figure 4. Returns from Mokelumne Hatchery release to lower Mokelumne River in 2014.<\/p><\/div>\n

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Figure 5. Coleman Hatchery 2014 smolt release group returns. Green dot is release site.<\/p><\/div>\n

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Figure 6. Coleman Hatchery 2014 smolt release group returns. Green dot is release site.<\/p><\/div>\n

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Figure 7. Green wedges are proportion of tags recovered in the American River in 2015 whose origin was the Mokelumne River Hatchery. Source: Pacific Fisheries Management Council.<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

A November 1, 2023 article, originally published in High Country News and later posted in Maven\u2019s Notebook, describes the practice of trucking juvenile salmon from hatcheries for release in salt water as a \u201cculprit,\u201d stating:\u00a0 According to a growing body … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[15,5],"tags":[],"class_list":["post-4449","post","type-post","status-publish","format-standard","hentry","category-bay-delta","category-hatcheries"],"jetpack_featured_media_url":"","jetpack-related-posts":[],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=\/wp\/v2\/posts\/4449","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4449"}],"version-history":[{"count":2,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=\/wp\/v2\/posts\/4449\/revisions"}],"predecessor-version":[{"id":4461,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=\/wp\/v2\/posts\/4449\/revisions\/4461"}],"wp:attachment":[{"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4449"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4449"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4449"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}