Dead fish a ‘nat­u­ral cy­cle’


Hun­dreds of tiny fish have been wash­ing up on Lake Taupo¯ beaches?

James Bar­nett from the Depart­ment of Con­ser­va­tion’s Taupo¯ Trout Fish­ery man­age­ment says the dead fish are no cause for alarm. ‘‘This is a nat­u­ral oc­cur­rence. ‘‘It’s a cycli­cal event. The species in­volved is the com­mon bully, which spawns in the shal­lows dur­ing the sum­mer.’’

The deaths hap­pen ev­ery sum­mer, but nor­mally the deaths are spread out over a pe­riod of time, Bar­nett said.

‘‘In­creased water tem­per­a­tures, com­bined with the rigor of de­fend­ing their eggs, take a huge toll on bul­lies, re­sult­ing in large-scale deaths.’’

The bul­lies are an im­por­tant source of food for trout, help­ing sus­tain smelt dur­ing their lar­val stage and trout as adults, he said.

How­ever, the deaths are un­likely to af­fect trout pop­u­la­tions. ‘‘It’s a nat­u­ral food cy­cle: it shouldn’t have any sig­nif­i­cant im­pact at all,’’ Bar­nett said.

‘‘There will still be other gen­er­a­tions of bully that haven’t met sex­ual ma­tu­rity yet, which will come through.’’

The com­mon bully can be found through­out New Zealand.

‘‘They usu­ally have a sea-go­ing lar­val phase. How­ever, lake-based pop­u­la­tions have be­come es­tab­lished in many ar­eas, in­clud­ing Lake Taupo¯ .’’

The lit­tle fish wash­ing up on Lake Taupo¯ beaches will have died from warm sum­mer water tem­per­a­tures.

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