Redfish and Specks Benefit from Limited Weir Closings

[MathGeek]

Another important point in the science centers on the attraction vs. production debate in fisheries. One viewpoint stresses that conditions that attract a lot of fish (reefs usually) must provide a net benefit to the fish through increased forage production, because the fish are drawn to food sources. The counter point stresses that this may not always be true and should be empirically demonstrated in each case, because a number of negative effects are possible when fish congregate in high densities.

This debate has raged for decades with respect to red snapper and artificial reefs/oil platforms. The empirical data has just emerged in the past few years showing that artificial reefs actually increase production of red snapper, they do not simply attract red snapper that were fed by the Gulf food web that would be present without the artificial reefs/oil platforms.

We've found some surprising results when correlating oyster stocks to fish condition factors. As we had expected, the more benthic and demersal species (redfish, drum, gafftops) show significant positive correlations with oyster stocks, suggesting that healthy oyster reefs contribute significantly to the benthic food web in ways that benefit these species.

However, fish condition in spotted sea trout is negatively correlated with oyster stock assessments. This suggests the propensity for sea trout to congregate at reefs may not be benefiting them. Their design makes them less able to utilize benthic food resources compared with the other species, and there is likely strong competition for available resources near the reefs, since the fish density seems to be much higher there. When stocks are low, specks are forced to spread out over the entire estuary and may thrive better when chasing bait higher in the water column throughout the estuary than when competing with dense populations of fish near oyster reefs.

Natural selection in specks probably drives them toward oyster reefs for protection from predators rather than increased forage that they can utilize. But specks in Big Lake today probably face far fewer natural predators than Gulf inshore and near shore specks have faced over the past few thousand years.