crabs<\/a> – either alive with injuries or killed with some remains left behind.<\/p>\nThe team found no evidence of fish predators in the study, suggesting that mid-salinity rivers do offer a refuge from some predators.<\/p>\n
Dr. Hines said: \u201cWe were amazed to find that over our 37-year study, cannibalism accounted for all of the predation, and we found no fish predation on tethered crabs.”<\/p>\n
Study co-author Dr. Matt Ogburn, a research ecologist at SERC, said: \u201cWe\u2019ve recorded a few of the tethering experiments with a high-resolution sonar.<\/p>\n
![\"Young](\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAQAAAADCAQAAAAe\/WZNAAAAEElEQVR42mM8U88ABowYDABAxQPltt5zqAAAAABJRU5ErkJggg==\")
<\/p>\n
Scientists Eric Johnson (left) and Rob Aguilar pull in a net during a survey for fish, crabs and other aquatic life. (Smithsonian ERC via SWNS)<\/p>\n
By Talker<\/p>\n
\u201cIn the sonar videos, most fish didn\u2019t show any interest in the tethered crabs, and only adult crabs attacked them.\u201d<\/p>\n
The researchers found that the smallest crabs were the most vulnerable, and more than twice as likely to get eaten compared to medium or large juveniles.<\/p>\n
But in shallow waters they were far safer.<\/p>\n
In the experiment, a small juvenile crab was 60% to 80% likely to get eaten in deeper waters of 1.3ft to 2.5ft depth.<\/p>\n
But in the shallowest zones less than six inches deep , they were only about 30% likely to be cannibalised.<\/p>\n
The rule of safety in the shallows held true for larger juveniles as well.<\/p>\n
Scientists are working on a new stock-assessment model for blue crabs in the Chesapeake that is expected to come out later this year.<\/p>\n
<\/p>\n
An adult male blue crab attempts to cannibalize a smaller blue crab on a tether. (Smithsonian ERC via SWNS)<\/p>\n
By Talker<\/p>\n
They say the long-term data from the study can help make the new model more accurate – especially the discovery that most cannibalism is focused on smaller juvenile crabs.<\/p>\n
Dr. Ogburn said: \u201dKnowing that juveniles become less susceptible to cannibalism as they grow is important for getting the new model right.”<\/p>\n
But the shallow-water sanctuaries are at risk as seawalls, riprap – a layer of large stones to protect soil from erosion, and other shoreline-hardening projects are shrinking the nearshore territory where young blue crabs can escape.<\/p>\n
Invasions by non-native species – especially blue catfish – may also impact blue crabs and further diminish the shallow refuge areas, according to the the study.<\/p>\n
Dr. Hines added: \u201cThe nearshore shallows of the mid-salinity zone provide juvenile crabs with a crucial refuge habitat from cannibalism by large crabs.<\/p>\n
“With cannibalism so intense and predators in every region of the bay, protecting these nearshore habitats – and restoring them where they have been lost – is critical for stabilising blue crab numbers and protecting the blue crab fishery as a whole.”<\/p>\n","protected":false},"excerpt":{"rendered":"A basket of blue crabs caught during a survey by the Smithsonian Environmental Resarch Center. (Smithsonian ERC via…\n","protected":false},"author":2,"featured_media":541687,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[2837,49120,79952,13927,49,211357,48,195206,211360,211361,35995,8889,8636,211359,19903,35994,52788,72961,64420,211358,66,126214,23441,35997,10128],"class_list":["post-541686","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-animals","tag-aquatic-ecology","tag-biogeography","tag-biology","tag-ca","tag-callinectes-sapidus","tag-canada","tag-cannibalism","tag-chesapeake-bay","tag-crab","tag-earth-sciences","tag-ecology","tag-fish","tag-fisheries-science","tag-marine-biology","tag-natural-environment","tag-oceanography","tag-physical-geography","tag-predation","tag-refuge-ecology","tag-science","tag-seagrass","tag-stephen-beech","tag-systems-ecology","tag-zoology"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/541686","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=541686"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/541686\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/541687"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=541686"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=541686"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=541686"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}