Largemouth Bass Growth In Relationship To Annual Variations In Mean Pool Elevations In Lake Carl Blackwell, Oklahoma

The growth history of largemouth bass in Lake Carl Blackwell is described. Variation in annual increments in growth of largemouth bass age groups I-III are examined in relationships to mean annual water level 1962 through 1967, when the annual average lake level was declining. Weighted mean average total lengths (mm) to the end of each year of life, i.e., to annulus formation which occurred in May, were: 140 (I); 279 (II); 369 (III); 425 (IV); 462 (V); 485 (VI); 504 (VII); and 53 I (VIII). Growth in the first year was positively correlated (r=0.85, P<.035) to the average annual lake level. In the second year the relationship was negative (r = -0.95, P<.004), that is, annual increments in growth in the second year of life were inversely related to lake level. Growth increments in the third and fourth years also were negatively correlated with lake level but the correlation was non-significant (P>.05). It is hypothesized that first year growth declined with declining lake level because of a negative effect of the drawdown on littoral zone invertebrates upon which bass feed in the first year. Second year growth increased with declining lake levels because of greater vulnerability of forage fish to predation by the larger piscivorous bass. Comparisons were made of the growth history of largemouth bass in Lake Carl Blackwell with the Oklahoma average and median growth from other U.S. locations cited in the literature. Largemouth bass growth rates in Lake Carl Blackwell were about equal to growth rates in Missouri, Tennessee, Louisiana, California and other Oklahoma waters, but much better than growth rates in the northern tier states, Great Lakes, and northeastern states.

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