|Stewart, Heather - Mississippi State University|
|Allen, Peter - Mississippi State University|
Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2013
Publication Date: 1/23/2014
Citation: Stewart, H.A., Allen, P.J. 2014. Critical thermal maxima of two geographic strains of channel and hybrid catfish. North American Journal of Aquaculture. 76:104-111.
Interpretive Summary: Two geographic strains (Red River, North Dakota or northern and Delta Select, MS or sourthern) of channel catfish and their corresponding cross with a strain of blue catfish were tested for upper critical thermal tolerance (CTMax). The southern strain of catfish had a higher CTMax than the northern strain, and the southern hybrid strain of channel catfish had a higher CTMax than the northern hybrid strain. Further, both strains of channel catfish tolerated higher temperatures than the hybrid catfish. Therefore, there are geographic differences in temperature tolerance in channel catfish, there appears to be heritability to CTMax, and channel catfish have greater temperature tolerance than hybrid catfish.
Technical Abstract: Critical thermal maxima have been used extensively to provide physiologically and ecologically valuable reference points that identify early signs of thermal stress. In catfish pond culture, daily temperature maxima up to 36'C and daily fluctuations of as much as 6'Care observed. These extreme conditions will probably be exacerbated by the effects of global climate change. Channel Catfish Ictalurus punctatus have a broad natural distribution from southern Canada to northern Mexico. If regional genetic differences could cause strains with a southern distribution to have greater thermal tolerance than strains with a northern distribution, and consequently a greater critical thermal maximum, then hybrid catfish (Channel Catfish × Blue Catfish I. furcatus) strains might be expected to have greater critical thermal maxima than their respective Channel Catfish strains because Blue Catfish have a more southern range of distribution. To examine this, we quantified differences of acute thermal tolerance in two geographically distinct strains of Channel Catfish and their hybrid crosses with an industry standard strain of Blue Catfish. The catfish were subjected to water temperature increases of 2.0 ± 0.1'C · h-1 until they lost equilibrium. Standard length, which ranged from 162 to 320 mm, had a significant effect on survival, survival being greater in larger fish. The critical thermal maximum ranged from 38.6'C to 40.3'C. Southern Channel Catfish tolerated higher temperatures than northern Channel Catfish did, and both strains of Channel Catfish tolerated higher temperatures than their hybrid catfish strains did. This study indicates that geographically distinct catfish strains differ in acute thermal tolerance and suggests heritability for this trait, as evidenced by similar responses in Channel Catfish and their corresponding hybrid crosses with Blue Catfish.