Analysis of flathead catfish population parameters using spine versus otolith age data Jeffrey C. Jolley, Peter C. Sakaris, and Elise R. Irwin Alabama Cooperative Fish and Wildlife Research Unit

State Management Overview ~3 states have maximum size limits –MN: 1 over 24” –ND: 1 over 24” –TN: 1 over 34” ~21 states have creel limits ~10 states have minimum size limits –10”(Indiana – all species) – 25”(Mississippi – flatheads)

Population parameters Fish aging is generally required for proper assessment of fish populations Various aging techniques have been developed for catfishes Incorrect age estimates may lead to unintended management outcomes

Objectives Compare age estimates for two flathead catfish populations via two techniques –otoliths and spines Model and compare populations under varying management regimes using age data Model population growth using survival estimates derived from data

Flathead catfish (Pylodictus olivarus)

Methods Collection –Boat mounted electrofisher, Gillnets, hoopnets, trotlines, jug-lines, and slatboxes used to facilitate catches Aging –Otoliths and spines removed from all sacrificed fish –Recent studies indicate that otoliths are accurate for aging catfishes

Otolith Spine 892 mm; ~11-13 annuli seen 892 mm; Age-25 flathead catfish

Models Traditional fishery analysis –FAST (Slipke and Maceina 2000) –Jones (1957) modification of the Beverton-Holt equilibrium yield equation to compute yield (Y) Leslie matrix population modeling –PopTools v. 2.5 (Hood 2003) in Microsoft Excel®

PopulationAging Structure NumberMaximum Age Mean Age CoosaOtolith CoosaSpine OcmulgeeOtolith OcmulgeeSpine Results

ParameterValue Von Bertalanffy growth coefficientsL ∞ = 1137 mm; K = 0.089; t 0 = years Maximum age18 years Conditional natural mortality17% Conditional fishing mortality5% to 50% Log 10 (wt):log 10 (TL)coefficientIntercept = ; slope = 3.12 Age at sexual maturation5 years Fecundity-to-length regressionLog 10 (fecundity) = Log 10 (TL) – Percent of fish that are females43% for all age groups Percent of females spawning annually100% Minimum length limits254 mm, 381 mm, 508 mm, 635 mm Life history parameters Coosa River- Spines

ParameterValue Von Bertalanffy growth coefficientsL ∞ = 1137 mm; K = 0.059; t 0 = years Maximum age25 years Conditional natural mortality13% Life history parameters Coosa River- Otoliths

Yield – spines versus otoliths Coosa River

SPR – spines versus otoliths 29% decrease 18% decrease Coosa River

72% decrease #Memorable fish – spines versus otoliths Coosa River

ParameterValue Spines: Von Bertalanffy growth coefficients L ∞ = 1080 mm; K = 0.233; t 0 = years Maximum age15 years Conditional natural mortality24% Age at sexual maturation4 years Otoliths: Von Bertalanffy growth coefficients L ∞ = 1080 mm; K = 0.217; t 0 = years Maximum age16 years Conditional natural mortality23% Age at sexual maturation4 years Life history parameters Ocmulgee River- Spines versus Otoliths

Ocmulgee River – spines vs otoliths

Coosa River Ocmulgee River

Population Matrix Model Spines versus Otoliths – population growth modeled for Coosa and Ocmulgee flathead catfish –λ, population growth rate –Survival estimates of mature fish derived from catch-curves Assumptions –1:1 sex ratio, survival of YOY and juvenile fish constant –Coosa: age at maturity – 5 yrs –Ocmulgee: age at maturity – 4yrs –Fecundity adjusted for survival

Coosa survival-spines versus otoliths ANCOVA: t = 2.73, P=0.01, slopes were different

Population growth – spines vs otoliths

Ocmulgee survival-spines vs otoliths ANCOVA: t = -0.16, P=0.87, slopes were similar

Population growth – spines vs otoliths

Ocmulgee versus Coosa - Growth

Conclusions Spine derived age information may be adequate at times –Depends on the growth-characteristics of the population –Depends on management concern – maximum yield or trophy fish Otolith derived age information should be used for population growth models, –Especially when individuals in the population are slow- growing.

Thanks to Alabama Department of Conservation and Natural Resources M. Maceina D. DeVries Y. Brady J. McHugh S. Rider W. Benson B. Daniels C. Hayer G. Katechis K. Kleiner A. Nicholls M. Ross N. Trippel M. Nash