Redfish and Specks Benefit from Limited Weir Closings

[Duck Butter]

Originally Posted by MathGeek

Plumpness in animals depends not only on food intake, but on the balance sheet between food intake and energy expenditures.

It is very common for freshwater trout in mountain reservoirs to lose body condition over the spring and summer months (when most food is available) because their energy requirements are also a lot higher in the summer months. Conversely, it is common for freshwater trout in mountain reservoirs to gain body condition over the winter (when food is scarce), because their energy requirements are much lower.

Similarly, stream trout can lose body condition under high current conditions because the additional energy expenditures exceed the additional caloric intake.

With brackish species, osmoregulatory costs also factor in: salinity much higher or lower than the preferred range of a species significantly drives up metabolic costs.

A human counterexample would be an athlete losing BMI with the same caloric intake on which most office types would quickly gain BMI.



In the case of the weirs, the planet is planet earth. For additional weir openings to increase fish condition, the additional food needs to exceed the additional energy requirements of the change.

Opening the weirs in addition to the baseline opening may not provide a net gain in additional food at all if the net change in forage flow is negative.

Opening the weirs in addition to the baseline opening may provide additional food, but it may increase the metabolic costs by a larger amount. This seems more likely.

It's like giving away Big Macs on the top of a mountain with the parking lot at the bottom. The people eating the extra burgers would probably lose BMI.

seatrout (drum/apples) freshwater trout (salmonids/oranges) but anyhoo