Relative Abundance, Growth, and Mortality of Suwannee Bass in Four Florida Rivers

Abstract

In an effort to aid in the conservation of black basses, the relative abundance, growth, and mortality of Suwannee bass Micropterus notius and largemouth bass M. salmoides were estimated from four Florida rivers. Fish were collected by electrofishing in the four rivers during 2001 and 2002. Electrofishing catch per unit effort of Suwannee bass was highest in the Wacissa River (95.1 fish/h), intermediate in the Santa Fe River (22.6 fish/h), and lowest in the Withlacoochee (5 fish/h) and Ochlockonee rivers (1.9 fish/h). Catch per unit effort for largemouth bass was also highest in the Wacissa River (50 fish/h), intermediate in the Santa Fe (19.8 fish/h) and Ochlockonee rivers (17.1 fish/h), and lowest in the Withlacoochee River (9.9 fish/h). Mean total length (TL) at age across the four Suwannee bass populations was described by von Bertalanffy growth curves as TL = 386.1 · (1 − e−0.3733(age+0.7772)) for females and as TL = 324.1 · (1 − e−0.4735(age+0.6543)) for males. Mean TL at age across the three largemouth bass populations was also described by von Bertalanffy growth curves as TL = 644.2 · (1 − e−0.2064(age+0.9840)) for females and TL = 427.8 · (1 − e−0.3164(age+0.9991)) for males. Suwannee bass exhibited sex‐specific growth rates similar to those of largemouth bass, females experiencing more rapid growth and attaining larger sizes than males (F1, 564 = 20.39; P < 0.01). Suwannee bass total annual mortality (A) averaged 40%, ranging from 28% to 46%. Similarly, largemouth bass total A averaged 40%, ranging from 35% to 46%. The current Florida minimum length limit on Suwannee bass directs fishing mortality almost solely to females, but estimates of fishing mortality are needed to determine whether this is a concern for black bass with a small native range.

Proposed Standard Weight (Ws) Equation and Standard Length Categories for Suwannee Bass

“…Growth and relative abundance has been reported in a previous study for four of these populations (Bonvechio et al 2005). Given such a small sample size, no formal analyses could be performed, but anecdotal evidence shows that populations with lower abundance and faster growth tend to have higher condition.…”

“…Given such a small sample size, no formal analyses could be performed, but anecdotal evidence shows that populations with lower abundance and faster growth tend to have higher condition. For example, the upper Ochlockonee River population exhibited the best condition (mean W r ¼ 101) and had the fastest growth and lowest abundance of the rivers examined (Bonvechio et al 2005). Conversely, the Wacissa River population had the highest relative abundance and had slower growth but slightly lower condition (mean W r ¼ 96; Bonvechio et al 2005).…”

“…For example, the upper Ochlockonee River population exhibited the best condition (mean W r ¼ 101) and had the fastest growth and lowest abundance of the rivers examined (Bonvechio et al 2005). Conversely, the Wacissa River population had the highest relative abundance and had slower growth but slightly lower condition (mean W r ¼ 96; Bonvechio et al 2005). Future efforts should focus on assessing the growth of other populations and identifying the mechanisms influencing the growth, abundance, and condition of Suwannee bass throughout its range.…”

“…The Suwannee bass occurs in the Ichetucknee, Santa Fe, St. Marks, Suwannee, Wacissa, and Wakulla rivers of Florida, as well as the Alapaha, Ochlockonee, and Withlacoochee rivers of Florida and Georgia (Hellier 1967;Hurst et al 1975;MacCrimmon and Robbins 1975;Swift et al 1977;Cailteux et al 2002aCailteux et al , 2002bBonvechio et al 2005;Bonvechio and Freeman 2009). As a result of its limited geographic distribution, which roughly encompasses an area of 8,500 km 2 , the Suwannee bass is considered a species of special concern in both Florida (Gruver 2006) and Georgia (Georgia DNR 2010).…”

“…The development of standard assessment tools can be beneficial for the management and conservation of Suwannee bass and other rare species. Bonvechio et al (2005) assessed the age and growth of several Suwannee bass populations, but there is no W s equation or standard length categories for this species, which would provide a quick and easy tool for evaluating condition and size structure. Thus, the objectives of this study were to (1) develop W s equations using the traditional regression-line-percentile (RLP) and newer empirical-percentile (EmP) techniques, and (2) develop five standard length categories for the Suwannee bass.…”