Quote:
Originally Posted by "W"
Don't need weirs when fishing Sabine and on beach
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It is important to realize that the weirs being opened or closed only provides a focal point for locating fish in the short term, it does not magically make fish appear in the lake. In the long term, opening the weirs provides more forage to the fish in the estuary, but it is an open question whether opening the weirs 365 days a year would increase the available food supply by 1%, 5%, 10%, 50%, or 100%.
A few points of science may help people understand why how many fish they catch may not always be closely related to the health of the estuary. Back in April and May, there were lots of complaints and concerns that the sky might be falling because trout fishing was slow and the weirs had not been opened as often as some had desired. But there being few fish in the lake is only one of several possible explanations for low catch rates. More likely explanations (in light of available data) are that the fish had shifted patterns in pursuit of available forage and that the fish were not eager to bite what anglers were throwing at them.
Most anglers develop their fishing habits for specks aimed at specks chasing shrimp, mullet, and croaker and also aimed at the propensity for larger specks to seek oyster reef habitat in the spring. However, the cool spring and destruction of oyster reefs made the specks less predictable this year. Shrimp numbers were down (cool weather and closed weirs), and manhaden numbers were up (pogey plant closing). Cooler water temperatures and higher salinities also lowered speck metabolic rates so they did not need to feed as agressively to maintain body condition.
When we sampled fish condition in late May, the specks were in great shape, with an average of 106% of a healthy body condition. The fish were eating well compared with their metabolic demands. But we weren't seeing many anglers returning to the boat ramp with limits of fish. Limits of fish became more regular after the waters warmed up in June, because the increased metabolic demands of warmer water caused the fish to feed more aggressively. Some localized fish kills on bait may also have reduced the availability of age zero menhaden.
There is a strong theoretical basis to believe that the number of days the weirs are open will have a significant impact on the condition of fish in the estuary, and in the long term, increasing exchange between the marsh and the lake are important and should have measurable effects.
So far, we have four years of data. We can see the expected effects of temperature, salinity, oyster stocks, and interspecies competition in the available data, but the effects of the weirs are either too small to see or masked by confounding factors. This may be cleared up by additional years of data or access to LDWF data or by access to improved data regarding historical openings and closings of each water control structure.
But for now, it is hard not to think that most angler complaints about the weirs being open or closed result from confirmation bias and the tendency of open weirs concentrating the fish in a predictable location so that they are easier to catch.
Even a saltwater barrier or rocking the ship channel to maintain lower salinities in the lake will not produce the ideal trout fishery that is hoped for. Maintaining salinities below 10-15 ppt in the lower lake for most of the year would allow the weirs to be open for 150-200 days per year, but the lower salinities would also exert a high osmoregulation cost on specks which prefer salinities in the 25-35 ppt range. The specks in that scenario would face the trade-off between a higher metabolic burden to enter the lake and take advantage of the available forage from the open weirs and to remain in the ship channel and gulf which has a much lower metabolic burden.
Salinities below 10-15 ppt would favor redfish, black drum, and gafftops in the lake, because these fish are better adapted to mid range salinities and would have a lower metabolic burden in the lake. Salinity levels below 10 ppt would be great for keeping the weirs open, but at these levels, the health of the oyster reefs would also begin to be negatively impacted.