Cli­mate change sur­vival

Anglers Mail - - Anglers -

QWhat ef­fect is global warm­ing likely to have on fish spawn­ing?

Eileen Brooke, via email.

ACli­mate change is a huge and com­plex global prob­lem, which has wide-rang­ing so­cial and eco­nomic im­pli­ca­tions, as well as those re­lat­ing to the nat­u­ral en­vi­ron­ment, and what­ever cli­mate change de­niers say, it’s here, it’s hap­pen­ing, and it won’t go away.

Av­er­age tem­per­a­tures in the UK have risen by a de­gree since the 1970s, and ocean tem­per­a­tures by 1.5 de­grees since the 1980s, and even if emis­sions are cut dra­mat­i­cally with im­me­di­ate ef­fect, the level of green­house gases al­ready in the at­mos­phere means that fur­ther warm­ing is in­evitable.

Com­puter mod­el­ling based on cur­rent data sug­gests that win­ters in the UK will be­come wet­ter and sum­mers will be­come warmer. Wet­ter win­ters will in­crease the like­li­hood of flood­ing, which brings with it the po­ten­tial to re­shape river­ine habi­tat, and threaten the sur­vival of over­win­ter­ing fry.

Higher sum­mer tem­per­a­tures will re­sult in greatly re­duced river flows, poor ground­wa­ter re­plen­ish­ment, in­creased evap­o­ra­tion, in­creased sil­ta­tion, greater wa­ter en­rich­ment, re­duced di­lu­tion of pol­lu­tants, and re­duced oxy­gen sat­u­ra­tion. Over­all, it’s not a pretty pic­ture for the aquatic en­vi­ron­ment, with finely bal­anced ecosys­tems likely to be ad­versely im­pacted by a huge range of en­vi­ron­men­tal vari­ables.

As far as fish­eries are con­cerned, the cur­rent, big­ger pic­ture is fo­cussed more on the im­pact upon the com­mer­cially im­por­tant ma­rine and mi­gra­tory species than on our coarse species, but the im­pli­ca­tions are clear.

Cold­wa­ter ma­rine species, such as cod and had­dock, are al­ready mov­ing fur­ther north­wards, to stay within their eco­log­i­cal tem­per­a­ture range, and south­ern ‘in­vaders’ are be­gin­ning to push into UK wa­ters, in­clud­ing sar­dines, red mul­let and John Dory.

There are, how­ever, a few po­ten­tial ben­e­fits for an­glers, in­clud­ing the pos­si­ble reestab­lish­ment of a UK tuna fish­ery, but this has to be bal­anced by the po­ten­tial fail­ure of our At­lantic salmon fish­ery, due to dis­rup­tion of tem­per­a­ture-re­lated mi­gra­tion and spawn­ing, and the loss of vul­ner­a­ble and en­dan­gered species, such as the Euro­pean white­fish (powan/pol­lan).

As with all en­vi­ron­men­tal change, there will be some species that win and some that lose. With global warm­ing, all pre­dic­tions sug­gest that there will be far more losers than win­ners, and that works in all habi­tats right across the globe, not just in the aquatic en­vi­ron­ment.

Spawn­ing is just a small part of the over­all cli­mate change pic­ture, al­beit an im­por­tant one. As far as spawn­ing is con­cerned, the main short-term im­pact, as with ma­rine and mi­gra­tory species, will be upon those species at the ex­tremes of

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