Sal­mon in farms have hear­ing de­for­mity

Port Douglas & Mossman Gazette - - SPORT -

HALF of the world’s farmed At­lantic sal­mon have hear­ing loss which could be com­pro­mis­ing crit­i­cal re­stock­ing pro­grammes, ac­cord­ing to new re­search.

The re­port pub­lished in the jour­nal has re­vealed for the first time that the farmed sal­mon are 10 times more likely than fish in the wild to suf­fer from a de­for­mity of the ear­bone thought to be lead­ing to the hear­ing loss.

The sal­mon’s ears are es­sen­tial for hear­ing and bal­ance, so the find­ings are sig­nif­i­cant for the wel­fare of farmed fish as well as the sur­vival of cap­tive-bred fish re­leased into the wild for con­ser­va­tion pur­poses.

The Univer­sity of Mel­bourne-led study found that half of the world’s most farmed marine fish, At­lantic sal­mon, have a de­for­mity of the otolith or ‘fish ear­bone’, much like the in­ner ear of mam­mals. The de­for­mity was found to be very un­com­mon in wild fish.

Tormey Reimer, lead au­thor of the Univer­sity of Mel­bourne-led study, said: “The de­for­mity oc­curs when the typ­i­cal struc­ture of cal­cium car­bon­ate in the fish ear­bone is re­placed with a dif­fer­ent crys­tal form.

The de­formed ear­bones are larger, lighter and more brit­tle, and the way they per­form within the ear changes.”

“The de­for­mity oc­curs at an early age, most of­ten when fish are in a hatch­ery, but its ef­fects on hear­ing be­come in­creas­ingly more se­vere as the fish age. Our re­search sug­gests that fish af­flicted with this de­for­mity can lose up to 50 per cent of their hear­ing sen­si­tiv­ity,” she added.

De­formed ear­bones could also ex­plain why many fish con­ser­va­tion pro­grams are not per­form­ing as ex­pected.

Hear­ing loss may pre­vent fish from de­tect­ing preda­tors, and re­strict their abil­ity to nav­i­gate back to their home stream to breed.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.