Murray Cod - Conservation

Conservation

Murray cod were originally the most common large native fish in the Murray-Darling basin. Contrary to some fishery department literature, the first serious declines in Murray cod were caused by overfishing — extremely severe overfishing. In the latter half of the 1800s and the early 1900s, Murray cod — very large, very long-lived fish — were caught in unimaginable numbers by both commercial and recreational fishermen. For example, one commercial fishing operation commenced on the Murray River near Echuca in 1855, targeting Murray cod over hundreds of kilometres of river, and yet within eight years, grave concerns over the sustainability of this operation, and complaints about the near-absence of Murray cod in their heavily fished grounds, were being raised in the main state newspaper, The Argus. And yet fishing effort continued to increase in the region so that in the late 1880s and early 1890s, between 40,000 and 150,000 kg of mostly Murray cod (between 7,500 and 27,000 fish, at an average weight of 5.5 kg) were caught near Echuca. Similarly, in 1883, more than 147,000 kg of Murray cod were sent to Melbourne from just one river town (Moama). By the 1920s Murray cod had been overfished to the point where large-scale commercial fishing operations were no longer feasible. Recreational fishermen took similarly excessive hauls during this era, using rods and reels, handlines, setlines, drum nets, gill nets and even explosives, with hauls often either wasted or illegally sold. Perhaps this extreme overfishing and its impacts of wild Murray cod stocks is best summarised by a short article in the Register News (a South Australian newspaper) in 1929:

In 29 years 26,214,502 lbs (nearly 11,703 tons) of Murray cod has been eaten by the people of Melbourne. The Superintendent of Markets (Mr G. B. Minns) included these figures in a statement he made today pointing out that the supply was declining. In 1918, the peak year, 2,229,024 lbs was received at the market, but since 1921, when 1,101,520 lbs was sent to Melbourne, supply has decreased. Last year it was only 551,040 lbs .

Incredibly, 20 years later the aquatic ecologist J.O. Langtry was still compelled to criticise the extremely heavy, lawless, fishing pressure, in the form of both uncontrolled small-scale commercial fishing and rampant illegal fishing, he was confronted with in all reaches of the Murray River he investigated in 1949–1950.

Indeed, a thorough reading of historical newspaper articles and historical government reports reveals that the whole history of wild Murray cod between the mid–1800s and the mid–1900s was one of citizen agitation, government inaction, and ongoing stock decline. For decade after decade, riverside residents, commercial fishermen, recreational fishermen, local fisheries inspectors, fish retailers and others agitated in newspapers and other fora about the evidently, continuously declining Murray cod stocks, to be met in turn either with government denials, or conversely, with various ineffective inquiries into Murray cod stocks and fisheries, and various ineffective control measures. For decade after decade, debate about excessive fishing pressure, number of fishermen, number of nets, net mesh size, bag limits, minimum size limits and take of small cod, closed seasons and the taking of spawning cod full of eggs during spring, and other sundry issues, raged on and on without proper resolution, with fishing regulations either not amended, or amended and largely unenforced and completely ignored, and with heavy commercial, recreational and illegal fishing pressure continuing unrelenting and unabated. The end result was a Murray cod population, initially unimaginably abundant, continually fished down and down and down without pause, until in the early to mid 20th century a number of other factors such as river regulation (listed below) emerged to drive the species even further into decline. All of these drivers of decline have left this iconic Australian fish in a perilous situation. There are now grave concerns for the long term survival of wild Murray cod populations.

Although angler effects are sometimes disregarded in the overall picture today, recent population studies have shown that while all year classes are well represented up to the minimum legal angling size (now 60 centimetres in most states), above that size, numbers of fish are dramatically reduced almost to the point of non-existence in many waters. Some emphasis has been made of the results of two small surveys which suggested a majority of Murray cod are released by anglers. However, there are valid questions as to the representativeness of these surveys, these surveys do not explain the dramatic disappearance of large numbers of young Murray cod at exactly the minimum size limit, and most importantly, any emphasis on these surveys miss the fundamental point — as a large, long-lived species with relatively low fecundity and delayed sexual maturity wild Murray cod populations are extremely vulnerable to overfishing, even with only modest angler-kill. A tightening of fishing regulations for wild Murray cod, as referred to above, and a switch by fishermen to a largely catch and release approach for wild Murray cod would alleviate this problem.

Another issue is that Murray cod caught and released in winter, while developing their eggs, or in spring prior to spawning, resorb their eggs and do not spawn. This may be a minor issue compared to some of the other threats facing Murray cod, nevertheless, concerned fishermen try to avoid catching wild Murray cod at these times. At this point in time a closed season is in place for the spring spawning period, during which anglers are not allowed to target Murray cod, even on a catch and release basis.

State Government Fisheries departments support Murray cod populations by stocking with hatchery bred fish, especially in man made lakes. Important issues affecting restoration of cod populations, such as the need for spring floods and excessive angler take, although yet to be addressed, will be dealt with in the National Recovery Plan when it is completed.