Survival of Advanced‐Fingerlings of Florida Largemouth Bass Stocked in Small Florida Lakes

Abstract

Numerous stocking evaluations of pellet-reared advanced-fingerling (80-120 mm TL) Largemouth Bass Micropterus salmoides have assessed the contribution of stocked fish to the wild population, but few studies have quantified longer-term (1-2 years) survival. Hatchery researchers have developed spawning Florida Largemouth Bass Micropterus salmoides floridanus (hereafter, "Florida Bass") out of season (i.e., in fall), allowing for a similar-sized product to be stocked earlier in the spring. Managers are interested in whether poststocking survival is improved by new culture techniques and whether survival can be affected by conditioning (acclimating to the natural environment) the fish before stocking. In this study, we stocked 11 small (<100 ha) lakes in central Florida with pellet-reared advanced-fingerling (mean 105 mm TL) Florida Bass that were spawned out of season, and we conducted mark-recapture population estimates at 1 and 2 years poststocking to assess survival. In the second year of the study, four lakes were stocked a second time with two treatments of Florida Bass (naïve and conditioned) to test for the effects of conditioning the fish on survival within the stocked lakes in 0.1-ha predator-limited enclosures for 7 d. At 1 year poststocking, survival ranged from 0.0% to 8.2% (values were <2.5% for all but one lake) and averaged 1.8%. At 2 years poststocking, survival ranged from 0.0% to 2.4% and averaged 0.9%. From the restocked lakes in year 2, we found no effect of conditioning (P = 0.57) on the number of stocked Florida Bass that were caught at 1 year poststocking, and survival ranged from 0.1% to 1.5% for the naïve treatment and 0.2% to 1.4% for the conditioned treatment. Despite improved culture techniques and the attempt to acclimate the stocked fish to the wild, survival averaged <2% at 1 year poststocking. Knowledge of projected Florida Bass survival can help managers make informed stocking decisions that are more likely to meet their desired outcome.

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“…Although morphological alterations are visible to the naked eye, physiological alterations or deficiencies in the body’s nutrients pool remain subtle. Post-stocking survivability is below 10% for both smaller size-at-release (fry; [ 5 ]) or bigger-size-at-release (advanced fingerlings; [ 15 ]). The conditioning processes prior to release or good habitat conditions at release site are decisive factors for post-stocking survivability.…”

“…Lately, with the advent of ‘off-season breeding’, there has been some opportunity in overcoming some of these issues [ 14 ]. However, their captive feeding is mostly on second priority, hit-and-trial basis, often leading to morphological alterations and nutritional deficiencies [ 15 , 16 , 17 , 18 ]. They may cascade to undetected causal mortalities after release which is easy to be blamed on problems existing in the habitat or release site.…”

“…On the other hand, longer time spent in captivity and resulting behavioral deficits might impair survivability too [ 8 , 14 ]. A lack of acclimation or conditioning procedures might occur before release, (i.e., in-situ pen or cage-based rearing, pond rearing with natural food, adding complexities within hatchery rearing tanks, training to live feed, exposure to predators, and smell of injured conspecifics) [ 7 , 8 , 14 , 15 , 16 ]. Several studies confirm the ‘bigger is better’ hypothesis in the context of post-stocking chances of survivability (discussed later).…”