Cold Snap Kills Kosi Fish


COLD SNAP KILLS KOSI BAY FISH
For immediate release
fish one...
Ezemvelo KZN Wildlife (EKZNW) and the Wetland Authority report that following a sudden and unseasonal drop in temperature last week an estimated two thousand fish have died and been washed up on the banks of First Lake at Kosi Bay.
Over ninety percent of the fish are Natal stumpnose but small numbers of spotted grunter, kingfish, pouter and two seapike have also been found.
Most of the fish are just under half a kilogram but some of the stumpnoses are
well over one kilogram.
Although the fish died of natural causes, by the time they are washed ashore
they are inedible and the public is strongly advised not to remove them for any reason.
The EKZNW ecologist at Kosi Bay who has worked in the Kosi system for more than 20 years Mr Scotty Kyle, reported that the fish were probably caught in the shallow water of the lake when there was a sudden overnight drop of seven degrees Centigrade in water temperature.
This sudden drop in temperature is lethal to some species of fish already stressed by a reduction in salinity of water in certain parts of the Kosi Lake system due to recent rains.
Some of the fish may also have been trapped in the baskets of the traditional fish traps when the temperatures dropped.
These fish traps have been used in the Kosi system for over 700 hundred years.
Mr Kyle reports that fish die offs due to temperature drops happen
sporadically at Kosi Bay and Natal stumpnose are the species most often
affected.
Similar die-offs of fish have also occurred at times of high or low salinity in Lake St Lucia in the past when a sudden drop in temperature adds a further stress to certain fish species resulting in the deaths of fish caught in shallow water and is an entirely natural phenomenon.
Deeper water buffers fish against the negative effects of such temperature changes.
Such shock responses to temperature drop usually occur in Third Lake in winter but the present deaths show all the symptoms of temperature induced mortality.
The fish deaths come at a time of excellent catches in the traditional traps.
These traps mainly catch fish exiting the Kosi Lakes to the ocean and
EKSNW staff report that there was a mass emigration of many fish, mostly Natal stumpnose, associated with the cold weather, strong winds and rain of the past weeks.
Despite the die off and trap catches, monitoring of recreational angler
catches in the last two days show some excellent results indicating that
there are still many fish around and the die off appears to be restricted to First
Lake.
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