Saturday 23 April 2011

Banded Morwong begins the hard fight against a decline towards extinction



Distribution - Banded morwong inhabit exposed rocky headlands and coastal reefs, from Seal Rocks in NSW, throughout Victorian and Tasmanian waters to Robe in South Australia. They are also found in New Zealand, where they are known as red moki.
Size - They are the largest of the morwongs, reaching a maximum length of approximately 70 centimetres and 15kg in weight.
Characteristics - The reddish-silver body displays approximately 8 thick bands, which vary in colour from reddish-brown to almost black in juveniles. Banded morwong feed on reef-dwelling shellfish and crustaceans, however, they are caught by spearfishers more often than by line fishers. They are a highly regarded tablefish.
Confusing species - Banded morwong are similar in shape and colour to the red-lipped morwong. They lack the characteristic brown spots of the re-lipped morwong and the distribution of these species does not overlap.

It was inevitable that evidence of the impact of climate change on marine life would move away from corals and hard-shelled creatures and focus on fish.

As an edible fish the Banded Morwong forms part of Australia’s native food stocks.

On 17 April 2011 Nature Climate Change magazine published Tolerance limit for fish growth exceeded by warming waters by A. B. Neuheimer, R. E. Thresher, J. M. Lyle & J. M. Semmens which demonstrates that this fish is beginning to be adversely affected by increased seawater temperatures:

Our data demonstrate that increasing water temperatures have pushed a species past the point where warming is beneficial to growth, and suggest mechanisms for range contraction as a result of this increase. The distribution of any species is a function of local environmental conditions and the likelihood of spawning and subsequent recruitment of juveniles. For populations living at the warm-edge of their distribution, temperatures that surpass TP result in higher metabolic costs and less availability of energy for growth and reproduction. Declining growth rates are also likely to reduce fecundity and egg quality, both of which vary directly with female size in fish (see, for example, ref. 25), and increase the risk of predation and starvation. Additionally, the loss of large fish at high temperatures is expected, as thermal sensitivity (via oxygen supply restriction) increases with body size. All of these effects imply a reduction in the population’s recruitment success24 and productivity.


Photograph from Reef Watch Victoria

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