In the coming decades, warming ocean temperatures could stunt the growth of fish by as much as 30 percent, according to a new study in the journal Global Change Biology.
Environmental News Network (ENN) reports that the main driver behind this decline in size is that warmer water contains less oxygen.
According to the report, fish are cold-blooded animals and therefore cannot regulate their own body temperatures. So as oceans heat up, a fish’s metabolism accelerates to cope with the rising temperatures and they need more oxygen to sustain their body functions.
But fish gills do not grow at the same pace as the rest of their body, resulting in a decline of oxygen supply and in growth.
ENN reports that for every one degree Celsius of ocean warming, active fish like tuna could shrink by as much as 30 percent, the study found, while less-active species like brown trout may only shrink by 18 percent. Overall, the decline in size could reduce commercial fish catches by about 3.4 million tons for each degree of warming.
“Fish are constrained by their gills in the amount of oxygen they can extract from the water,” Daniel Pauly, the study’s lead author and a principal investigator with Sea Around Us, a University of British Columbia research initiative, told Nexus Media.
“With increasing temperatures, fish require more oxygen but get less,” he said.
Katika miongo ijayo, joto la bahari linaweza kupunguza ukuaji wa samaki kwa asilimia 30, kulingana na utafiti mpya uliochapishwa katika jarida la Global Change Biology. Kwa mujibu wa shirika la habari la Environmental News Network (ENN), sababu kuu ya kupungua kwa idadi ya viumbe hai ni kwamba maji yenye joto huwa na oksijeni kidogo. Kwa mujibu wa ripoti hiyo, samaki ni wanyama wenye damu baridi na kwa hiyo hawawezi kudhibiti joto la mwili wao wenyewe. Kwa hivyo, bahari zinapopanda joto, kimetaboliki ya samaki huongeza kasi ili kukabiliana na kuongezeka kwa joto na wanahitaji oksijeni zaidi ili kudumisha kazi zao za mwili. Lakini matumbo ya samaki hayakua kwa kasi sawa na sehemu nyingine za mwili wao, na hivyo kupunguza ugavi wa oksijeni na ukuaji. Kwa kila digrii moja ya joto la bahari, samaki kama tuna wanaweza kupungua kwa asilimia 30, wakati spishi zisizo na shughuli nyingi kama trout zinaweza kupungua kwa asilimia 18 tu. Kwa ujumla, kupungua kwa ukubwa kunaweza kupunguza samaki wanaovuliwa kwa biashara kwa takriban tani milioni 3.4 kwa kila kiwango cha joto. "Samaki wanalazimika kwa gills yao katika kiasi cha oksijeni wanaweza kutoa kutoka maji, ""Daniel Pauly, mwandishi wa utafiti wa kuongoza na mtafiti mkuu na Bahari Around Us, Chuo Kikuu cha British Columbia utafiti mpango, aliiambia Nexus Media." "Kwa kuongezeka kwa joto, samaki huhitaji oksijeni zaidi lakini hupata oksijeni kidogo", alisema.