Quote:
Originally Posted by dmtfish
OK, I get what you mean by the average BMI. IMO the estuary is too large to make an assumption that even a large percentage of the fish caught and measured spent at least some point in their life near the wiers. You have measured some of my fish in the past, but I can't remember if you asked where the fish were caught. Maybe this would help develop your hypothesis, that is, in future samplings ask the angler where the fish were caught. Assuming your hypothesis is correct, it may be useful to break down the data into groups, say fish caught at wiers, near the wiers on east bank, west cove, north end, etc... Then compare the data to see if indeed fish near the wiers have a lower body mass.
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Most available data show that over a three month period, fish are all over the estuary, and the conditions (food availability, salinity, temperature, exertion) over the 90 day window before fish are caught have a significant impact on body condition. Knowing where a fish was caught, just tells us where it was that day. Knowing where a fish was for the 90 days before it was caught would require outfitting a bunch of fish with acoustic telemetry and then having enough of those fish caught and returned to measure their weight. But then one needs to assume that adding the acoustic device did not impact the condition of the fish (unlikely).
Since spatially resolving where a specific fish has been over the past 90 days is a very tricky deal, one generally needs to develop methods for testing hypotheses which does not depend on the locations of each specific fish over the past 90 days. Perhaps a more approachable method to test this hypothesis would be in a laboratory where groups of fish are exposed to the different levels of current with the same amount of food. This would enable quantifying how much fighting a given current impacts body condition. These kinds of studies have been done in freshwater trout. But the lab study would only show that the hypothesis is plausible. A sonar study could estimate the biomass of fish in different current zones of the weirs at different times. If a significant fraction of the speck and redfish biomass were coming to the weirs and in locations where they were fighting the current, that would be much more compelling support for the hypothesis than angler reports regarding where specific fish were caught.