study<\/a> in Science.<\/p>\nSeveral large tuna species and sharks, known as \u201cmesothermic\u201d species for the way their bodies run hot, require more fuel to maintain their temperature and are thus confronting a \u201cdouble jeopardy\u201d of warming oceans and declining food, mainly from overfishing. As water temperatures climb, these species will be forced to relocate to cooler waters.<\/p>\n
\u201cIf you\u2019re a shark, you can\u2019t just pop down to the supermarket and buy more food,\u201d said Nick Payne, lead author and associate professor at Trinity College Dublin in Ireland. \u201cWe\u2019re seeing animals move with climate change in every biome on land and in the sea; this is just another example of that mechanism.\u201d<\/p>\n
From South Africa\u2019s powerful great whites to Ireland\u2019s filter-feeding basking sharks, these mesotherms burn nearly four times as much energy as their cold-blooded counterparts, whose body temperatures match the surrounding water. As oceans warm, these species must slow down, alter their blood flow or dive to cooler temperatures, all while hunting for an ever-dwindling food supply.<\/p>\n
A rare group comprising fewer than 0.1 percent of all marine life, mesothermic fishes \u2014 also including thresher and porbeagle sharks \u2014 trap metabolic heat to keep their bodies warmer than surrounding seawater. This has been evolutionarily key to enabling higher swimming speeds, enhanced predation, and their long-distance migrations.<\/p>\n
However, as fish grow larger, their bodies generate heat faster than they can shed it. This mismatch \u2014 driven by the physics of surface area and heat retention \u2014 triggers the overheating dilemma in warmer waters.<\/p>\n
While some species like Atlantic bluefin tuna can temporarily boost their heat loss or dive to colder waters, the suitable habitats for mesotherm species will shrink as larger swaths of oceans become inhospitably hot. This will be especially the case during summer months when sharks will experience increased competition for prey.<\/p>\n
This will disrupt ecosystems as mesotherms are typically apex predators that exert disproportionate control on species below them in the food chain, said Edward Snelling, coauthor and physiologist at the University of Pretoria.<\/p>\n
\u201cThese species are being pushed closer to their physiological limits, which could have consequences for where they can live and how they survive,\u201d said Snelling in a press release. \u201cThese animals are already operating on a tight energy budget, and climate change is narrowing their options even further.\u201d<\/p>\n
Using tiny sensors on a range of fish, including basking sharks weighing over 3 tons, researchers calculated how much heat fish produce and lose in real time. From this, they calculated that a one-ton warm-bodied shark may struggle to remain in waters above 62.6 degrees Fahrenheit\u00a0 (17 degrees Celsius) without taking counter measures. Discovering these \u201chidden heat budgets\u201d could prove critical to any hope of conserving them or mapping protection areas, researchers said.<\/p>\n
In South Africa, the stakes are both ecological and cultural. Here, great whites have emerged as a \u201csentinel species\u201d: When their patterns change, it signals a deeper shift in the marine ecosystem.<\/p>\n
While long sensationalized as feared predators, they\u2019ve increasingly become icons of marine conservation and ecotourism, said Stephanie Nicolaides, a marine conservation researcher at the University of the Western Cape. \u201cMany local and international conservation narratives now position the great white not as a villain, but as a keystone species essential to maintaining ocean health,\u201d Nicolaides said.<\/p>\n
Declines of great white sightings in False Bay, Mossel Bay, and Gansbaai, however, are multifaceted. Though thermal relocation may be a contributor, their population decline is also linked to a history of overfishing, shark netting, and habitat destruction.<\/p>\n
Indeed, though warming waters heighten mesotherms\u2019 vulnerability worldwide, other manmade harms exert the most danger. \u201cIf we had to say what is the one thing that we need to urgently address for these animals, it\u2019s the fishing problem,\u201d said Payne. \u201cThe most acute, urgent crisis these animals face is from overfishing, and particularly now from bycatch.\u201d<\/p>\n
Bycatch refers to fish and other marine animals caught unintentionally by fishermen using huge nets or long lines baited with thousands of hooks.<\/p>\n
History, however, offers a grim precedent for physiological vulnerability itself. Fossils of extinct warm-bodied species \u2014 like the infamous Megalodon shark, which reached almost 60 feet long \u2014suggest they suffered disproportionately during past ocean temperature increases as they likely struggled to secure food to fuel their large, warm bodies.<\/p>\n
\u201cToday\u2019s oceans are changing at unprecedented speeds,\u201d Payne said. \u201cThe alarm bells are ringing loudly at this point.\u201d<\/p>\n
\u2014Johnny Sturgeon, Inside Climate News<\/p>\n
ALSO ON YALE E360<\/strong><\/p>\nSea Star Murder Mystery: What\u2019s Killing a Key Ocean Species?<\/strong><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"The evolutionary edge that fueled great white shark dominance for millions of years could soon become its greatest…\n","protected":false},"author":2,"featured_media":448680,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[77],"tags":[35592,197840,86933,442,18,39151,19,17,197842,10734,197841,133,197844,197845,197843],"class_list":["post-448679","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-apex-predators","tag-basking-sharks","tag-body-temperatures","tag-climate-change","tag-eire","tag-great-white-shark","tag-ie","tag-ireland","tag-nick-payne","tag-oceans","tag-porbeagle-sharks","tag-science","tag-sentinel-species","tag-stephanie-nicolaides","tag-warmer-waters"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/116450002502284156","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/448679","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=448679"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/448679\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/448680"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=448679"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=448679"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=448679"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}