Evaluation of an Unsuccessful Brook Trout Electrofishing Removal Project in a Small Rocky Mountain Stream.

In the western United States, exotic brook trout Salvelinus fontinalis frequently have a deleterious effect on native salmonids, and biologists often attempt to remove brook trout from streams by means of electrofishing. Although the success of such projects typically is low, few studies have assessed the underlying mechanisms of failure, especially in terms of compensatory responses. A multiagency watershed advisory group (WAG) conducted a 3-year removal project to reduce brook trout and enhance native salmonids in 7.8 km of a southwestern Idaho stream. We evaluated the costs and success of their project in suppressing brook trout and looked for brook trout compensatory responses, such as decreased natural mortality, increased growth, increased fecundity at length, and earlier maturation. The total number of brook trout removed was 1,401 in 1998, 1,241 in 1999, and 890 in 2000; removal constituted an estimated 88% of the total number of brook trout in the stream in 1999 and 79% in 2000. Although abundance of age-1 and older brook trout declined slightly during and after the removals, abundance of age-0 brook trout increased 789% in the entire stream 2 years after the removals ceased. Total annual survival rate for age-2 and older brook trout did not decrease during the removals, and the removals failed to produce an increase in the abundance of native redband trout Oncorhynchus mykiss gairdneri. Lack of a meaningful decline and unchanged total mortality for older brook trout during the removals suggest that a compensatory response occurred in the brook trout population via reduced natural mortality, which offset the removal of large numbers of brook trout. Although we applaud WAG personnel for their goal of enhancing native salmonids by suppressing brook trout via electrofishing removal, we conclude that their efforts were unsuccessful and suggest that similar future projects elsewhere over such large stream lengths would be costly, quixotic enterprises

Corrosion Rates and Compression Strength of White Sturgeon‐Sized Fishing Hooks Exposed to Simulated Stomach Conditions

Field reports indicate that many White Sturgeon Acipenser transmontanus ingest hooks internally, but the length of time required for hooks to corrode, facilitating passage through their digestive system, is not well understood. Using a buffered acidic solution to simulate stomach conditions, a laboratory experiment was used to estimate the speed at which sturgeon-sized hooks (2.0-mm wire diameter) lost weight and compression strength and to evaluate whether loss of hook weight and compression strength was affected by hook abrasion, such as may occur when baited hooks are ground between hard food items in the gizzard of a sturgeon. After 399 d, hooks lost an estimated 34% of their weight and 70% of their compression strength. Abrading the hooks with stones before and throughout the study accelerated weight loss by 34% (after 399 d) compared with nonabraded hooks but did not accelerate the loss of compression strength. Abrasion increased the variability between hooks in weight loss but not in compression strength. Regardless of hook abrasion, the compression strength of some hooks was reduced essentially to 0 N within 1 year of constant exposure to stomach-like acidic conditions