It’s too hot for the fish

Port Douglas & Mossman Gazette - - FRONT PAGE -

A TEAM of re­searchers from the ARC Cen­tre of Ex­cel­lence for Coral Reef Stud­ies at James Cook Univer­sity has shown that ocean warm­ing may make some large reef fish feel the same way.

Re­searcher Dr Ja­cob Jo­hansen said that fish rely on swim­ming for al­most all ac­tiv­i­ties nec­es­sary for sur­vival, in­clud­ing hunt­ing for food and find­ing mates.

‘‘How­ever, global warm­ing may re­duce the swim­ming abil­ity of many fish species, and have ma­jor im­pacts on their abil­ity to grow and re­pro­duce,’’ he said.

Dr Jo­hansen said re­search aimed at un­der­stand­ing the im­pact of global warm­ing on the com­mer­cially im­por­tant fish species, coral trout, re­vealed that in­creas­ing ocean tem­per­a­tures may cause large fish to be­come lethar­gic, spend­ing more time rest­ing on the bot­tom and less time swim­ming in search for food or re­pro­duc­tive op­por­tu­ni­ties.

He said that the study he and his col­leagues had un­der­taken showed that even when in­di­vid­u­als do muster up enough en­ergy to swim around, they swim at much slower rate. This lower ac­tiv­ity is likely to di­rectly im­pact their abil­ity to catch food, or visit spawn­ing sites.

‘‘The loss of swim­ming per­for­mance and re­duced abil­ity to main­tain im­por­tant ac­tiv­i­ties, like mov­ing to a spawn­ing site to re­pro­duce, could have ma­jor im­pli­ca­tions for the fu­ture dis­tri­bu­tion and abun­dance of th­ese species," Dr Jo­hansen said.

Pro­fes­sor Mor­gan Pratch­ett said that the changes to ac­tiv­ity pat­terns and swim­ming speeds "may di­rectly in­flu­ence where we will find th­ese species in the fu­ture and how many we are able to fish sus­tain­ably’’.

But all is not lost, Dr Jo­hansen said, as there was some ev­i­dence that coral trout may be able to adapt to in­creas­ing tem­per­a­tures. ‘‘Pop­u­la­tions from the north­ern re­gion of the Great Bar­rier Reef were a lit­tle bet­ter than south­ern pop­u­la­tions at tol­er­at­ing th­ese con­di­tions,’’ he said. ‘‘Coral trout is one of the most im­por­tant fish­eries in the South-East Pa­cific.’’

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