{"id":1271,"date":"2016-11-11T10:31:56","date_gmt":"2016-11-11T18:31:56","guid":{"rendered":"http:\/\/calsport.org\/fisheriesblog\/?p=1271"},"modified":"2016-11-11T10:31:56","modified_gmt":"2016-11-11T18:31:56","slug":"does-the-central-valley-need-a-predator-removal-program","status":"publish","type":"post","link":"https:\/\/calsport.org\/fisheriesblog\/?p=1271","title":{"rendered":"Does the Central Valley Need a Predator Removal Program?"},"content":{"rendered":"

The Columbia River Pikeminnow Sport Reward Program<\/a> just finished another year.\u00a0 A near-record 200,000 adult pikeminnow were harvested and $1.7 million rewards paid.\u00a0 The goal of the program is to harvest 10-20% of the population each year to reduce the population about 50%.\u00a0 Harvest rates in recent years reached as high as 17% as compared to this year\u2019s 11%.<\/p>\n

So why after 25 years is the program still harvesting near-record numbers of pikeminnow?\u00a0 The likely reason is that the program is not based on sound science.\u00a0 The Columbia pikeminnow population dynamics likely are best described with a standard Ricker-Type Population Model (see chart below), with reduced recruitment of young at high adult population levels because of competition and cannibalism.\u00a0 The introduction of a light harvest can actual increase recruitment of young by reducing competition and cannibalism, with the increased recruitment replacing the harvest, even providing a constant harvest or yield.\u00a0 This is how fishery quotas may be sustained year after year, such as in Alaska\u2019s Bristol Bay Sockeye salmon fishery.<\/p>\n

This same dynamic likely applies to pikeminnow and some other predators in the Central Valley.\u00a0 Pikeminnow are likely near their saturation level in the Central Valley.\u00a0 Any light harvest such as from a sport-reward or removal program would likely have little or no effect.\u00a0 Increasing harvest on non-native predators like largemouth bass by reducing sport-fishing harvest regulations would likely also have a limited benefit.\u00a0 However, striped bass, the most popular sport fish in the Delta, has a population that is already seriously depressed by long-term loss of juveniles to water diversions.\u00a0 Striped bass may respond more directly to increased harvest, further reducing recruitment and further depressing the population.<\/p>\n

Thus the species composition of fish that eat other fish could change, satisfying those who vilify stripers and infuriating those who fish for them.\u00a0 But the potential for reduced overall loss of juvenile salmon or other native species that might follow from \u201cpredator removal\u201d is far more complex and questionable than its proponents maintain.<\/p>\n

\"Ricker-type

Ricker-type stock-recruitment population dynamics model that likely applies to Columbia River and Sacramento River pikeminnow populations<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

The Columbia River Pikeminnow Sport Reward Program just finished another year.\u00a0 A near-record 200,000 adult pikeminnow were harvested and $1.7 million rewards paid.\u00a0 The goal of the program is to harvest 10-20% of the population each year to reduce the … 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":[15,25,16],"tags":[],"class_list":["post-1271","post","type-post","status-publish","format-standard","hentry","category-bay-delta","category-pikeminnow","category-striped-bass"],"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\/1271","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=1271"}],"version-history":[{"count":3,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=\/wp\/v2\/posts\/1271\/revisions"}],"predecessor-version":[{"id":1275,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=\/wp\/v2\/posts\/1271\/revisions\/1275"}],"wp:attachment":[{"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1271"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1271"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/calsport.org\/fisheriesblog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1271"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}