Boycott the S.T.A.R.: Redfish starving in Big Lake
Red Drum Are Starving in Calcasieu Lake, Especially Bull Reds
As it happens, my colleagues and I have weighed and measured many hundreds of fish caught in Calcasieu Lake in 2011, 2012, and 2013. This large data set allows assessment of fish health by quantifying the ratio of a fish's actual weight to its expected weight based on its species, length, and time of year. This ratio is called the relative condition factor, Kn. A Kn = 1.0 is a healthy fish whose weight is the same as the typical weight of that species and season based on a large statewide data set of thousands of fish. Relative condition factors less than 1.0 are fish that are overly thin, often because of insufficient forage. Kn = 0.9 would be 90% of the expected weight (a fish that should weigh 3.0 lbs only weighs 2.7 lbs).
The attached graph shows mean condition factors for red drum from Calcasieu Lake by length class and year. You can see that most length classes and years are thin, showing an insufficient food supply for the population of fish, and that the larger red drum are having a particularly hard time maintaining body condition. As condition factors drop from 1.0 to 0.8, both fecundity rates and survival rates decrease dramatically. (Being 10-20% underweight significantly decreases the number of eggs and also puts energy reserves dangerously low.) Keep in mind that the graphs show the mean values. About half the fish in any group are thinner than the mean, and these fish are strongly at risk.
It takes some work and careful interpretation to discern from the data whether the most likely cause of the poor condition is the destruction of oyster reefs, the management of the weirs, saltwater intrusion, change in speck limit, erosion, or some other factor. Analysis of similar data for four species (red drum, black drum, gafftops, and specks), combined with the healthy relative condition factors observed by the USGS before 2005 and data from other locations suggests that oyster reef destruction is likely the strongest contributor to decline of body condition in redfish.
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