Originally Posted by MathGeek
Interestingly, Louisiana recently adopted (in 2006) a spatially-explicit management plan for Calcasieu Lake. The premise of this management decision, which included a reduction in daily bag limits and imposition of a slot limit, was to ‘preserve’ the renowned trophy-fishery for spotted seatrout in Calcasieu Lake. However, the decision to enact this regulation was based exclusively on socio-economic factors, rather than the biological status of the subpopulation. In fact, no formal stock assessment was conducted as part of the decision-making process. Thus, the status of the subpopulation (stock) was largely unknown (i.e., overfished or not?) at the time regulations were changed. While perhaps setting a bad precedent for fisheries management (i.e., making a decision based purely on socioeconomic reasons), this situation affords a unique opportunity to evaluate the response of spotted seatrout to a spatially-explicit (estuarine-scale) regulations change (i.e., adaptive management, sensu Hilborn and Walters 1992).
from Callihan PhD thesis LSU 2011 p. 182
Note that this 2011 PhD dissertation not only says that the rule changes were not justified by biological considerations, it also says that the rule changes afford an opportunity to evaluate the response of the spotted seatrout population to the rule changes.
In other words, the assertion is that current assessments of the spotted seatrout population in Big Lake would be measuring the impact of lowering of the limit and slot rather than other things like hurricane Rita or oyster harvesting which have been asserted by others in the discussion as potentially confounding factors. The dissertation studies the impact of changes in salinity and meteorological effects of things like tropical storms, and yet it concludes that impact of the regulation change can be measured through standard stock assessment methods.
And this is not only the opinion of the author, Dr. Jody Callihan, as the thesis was carefully reviewed by his thesis advisor, Dr. Jim Cowan, a Professor in the Department of Oceanography and Coastal Sciences at LSU. Dr. Cowan is a national leader in the biology of estuarine fishes having authored dozens of papers, overseen millions in research dollars, and served on the editoral board of several prestigious fisheries journals. Dr. Callihan's PhD Dissertation was also reviewed and approved by Dr. Jaye E. Cable, now a Professor in Marine Sciences at UNC-Chapel Hill and Dr. James Geaghan, Professor and Dept. Head in the LSU Dept. of Experimental Statistics.
The observation that there are too many spotted sea trout relative to their available food sources is much firmer than the assignment of a definitive cause. The biologists above seem to think that the limit change would have the greater impact on results of stock assessments after the limit change. Some contributors in this discussion think the oysters and tropical storms need to be considered as well.
With respect to whether or not it is a wise idea to change the limits back to 25, the cause(s) of the decline in average body condition and growth rates are not particularly important. Thinning the herd so there are less trout relative to their food supply is a sound management strategy given the fact that there are currently too many trout relative to the available food.
The majority of fish are caught by the minority of anglers. If raising the limit to 25 doesn't bring the population under control sufficiently to restore historical growth rates and fatness of trout in the estuary, then further steps can be considered.
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