Date of Award
Master of Science (MS)
Dr. William Stark
The introduction of a new fish species into an aquatic ecosystem can bring about many challenges for fisheries managers. Questions might arise for the manager regarding the initial sportfish survival rate, grow rate, reproduction and recruitment, and what kind of impact will the introduction have on the already established populations found in the water body. A new population of fish is often protected using length limit regulations, allowing biologists to gain insight on whether the population will be self-sustaining or in need of periodic stockings. Age and growth information is used to understand population dynamics, estimate annual mortality and recruitment, and generate insight on which abiotic and biotic factors might influence growth rates; often associated with survival, the faster you grow the less susceptible you are as an individual to being consumed. Growth rate determination requires the extraction of hard structures from individual fish within a robust sample of the population. Selection of hard structures used for aging a fish species depends on the structure’s ability to provide accurate and precise age estimation. Otoliths have emerged as the hard structure of choice to generate precise age estimates but require sacrificing individuals. I chose to use pectoral fin rays to estimate ages of Blue Catfish (Ictalurus furcatus) from two water bodies in Kansas to estimate whether pectoral fin rays generate usable data and minimize unnecessary mortality associated with the harvest of otoliths.
The Blue Catfish was introduced in Wilson Reservoir in 2006 and Lovewell Reservoir in 2010 with a shared management goal of establishing trophy fisheries. In 2016, I collected pectoral fin rays from 116 individuals from Lovewell Reservoir and 165 Blue Catfish from Wilson Reservoir and sectioned them with a novel approach that allowed me to conduct an age and growth analysis for both populations. The objective was to estimate the trophy potential of these populations based on growth rates.
The Wilson Reservoir population of Blue Catfish had 5 of 11-year classes were represented in the sample; All 7 years since the initial stocking were represented in Lovewell Reservoir samples. Only the Blue Catfish in Lovewell Reservoir has begun to recruit naturally and produce individuals surpassing the minimum length limit of 889 mm. The population in Wilson Reservoir exhibit slower growth rates compared to Lovewell Reservoir and individual growth rates slow down after fish reach 520 mm. Under current conditions, the Blue Catfish population at Lovewell Reservoir is likely more suitable for trophy management, due to natural reproduction and higher growth rates compared to the Wilson Reservoir population. However, Blue Catfish populations oftentimes take decades to realize trophy potential. Therefore, further analysis is needed to determine the underlying factors that lead to relatively poor growth of Blue Catfish at Wilson Reservoir.
Flores, Ernesto, "Size and Age Structure of Introduced Populations of Blue Catfish (Ictalurus furcatus) in Two Kansas Reservoirs and Implications for Management" (2019). Master's Theses. 3129.
Copyright Ernesto Flores 2019