No abstract

The efficiency and delayed mortality caused by a new gastric lavage device was evaluated for use on largemouth bass Micropterus salmoides. A 12‐V electric pump was specially fitted to flush stomach contents from largemouth bass larger than 200 mm. The device was easily operated by a single person and removed more than 90% of stomach contents. The lavage technique caused no immediate mortality of largemouth bass. Delayed (7‐d) mortality of largemouth bass undergoing gastric lavage was not significantly different from that of controls. Further, mortality did not vary significantly with body length. Overall, the technique appears to be a viable method for rapidly collecting stomach contents from a broad size range of largemouth bass while causing minimal initial and delayed mortality.

The influence and relative importance of fine sediment on wild brook trout (Salvelinus fontinalis) population size was assessed. Brook trout production in headwater streams was inversely proportional to substrate permeability in one of two years, suggesting substrate composition influenced production. Results suggest the critical fine sediment size for brook trout in this study, is between 0.063 mm and 1.0 mm. Further, fine sediment (< 0.063 mm) should not exceed 0.6-1.0% of spawning substrate, or negative population effects may be incurred. Under normal flow conditions, fine sediment was a principal determinant of juvenile trout abundance relative to other physical and biological factors. Adult trout abundance was principally a function of stream discharge, and was potentially further influenced by fine sediment impacts on juvenile recruitment. Spatially restricted food resources, created by drought-induced low flows in year 2 of the study, are believed to have overpowered mechanisms influencing trout abundance under normal flows.

We examined the influence and relative importance of fine sediment on wild brook trout (Salvelinus fontinalis) populations in a forested watershed. Brook trout spawning substrate was generally comprised of 75% particles < 32 mm, with approximately 27% < 4.0 mm. Brook trout production was inversely proportional to substrate permeability in one of two years, suggesting substrate composition was influential in regulating recruitment. In that year, age-0 brook trout abundance was negatively influenced by the amount of fine sediment < 0.063 mm. We identified that for brook trout the critical fine sediment size influencing recruitment as between 0.063 and 1.0 mm. The lack of a relationship between age-0 brook trout recruitment and abundance in a second year was thought to be the consequence of severe drought causing fine sediment levels to exceed 1% < 0.063 mm in spawning substrate in all streams. Habitat variables were not related to age-0 brook trout abundance or biomass suggesting that under normal flow conditions, fine sediment was a principal determinant of juvenile trout abundance relative to other physical and biological factors.

Alabama bass, Micropterus henshalli Hubbs & Bailey, are the dominant sportfish of Allatoona Reservoir, Georgia, USA, but no population assessment has been conducted. Thus, growth and total annual mortality were estimated in spring 2005, and a tagging study was conducted in 2006 and 2007 to estimate angler exploitation. These data were used with an age‐structured model to assess performance of a 356‐mm minimum length limit (MLL), a 406‐mm MLL and a 330‐ to 406‐mm protected slot length limit (SLL) compared to the present harvest regulation of no MLL. Mean annual exploitation varied from 12 to 22% each year and was generally highest for fish > 330 mm; total annual mortality was 44%. Models predicted a 49–153% increase in numbers of Alabama bass reaching 432 mm, a 22–66% decline in numbers harvested and only moderate declines in yield (5–25%) with the alternative harvest regulations compared to current conditions. The SLL may be an acceptable compromise to allow Allatoona Reservoir anglers to still harvest fish while also improving Alabama bass size structure.