Evaluation of Short‐Term Exposure to High Temperature as a Tool to Suppress the Reproductive Development of Channel Catfish for Aquaculture

Abstract

Short-term exposures to elevated temperatures reduce germ cell numbers in the gonads of some fishes, suggesting that heat treatment may be a viable method for delaying or suppressing reproductive development in cultured fishes. The objective of this study was to determine the effects of high temperatures on early gonadal development in channel catfish Ictalurus punctatus. Twenty-three-day-old (after hatching) channel catfish were exposed to temperatures of 27ЊC (control), 34ЊC, and 36ЊC for 4 weeks. Groups of 250 fry were placed in individual 152-L glass aquaria with external biofilters, and four replicated aquaria were used per temperature treatment. Water temperature was regulated with submersible heaters. At the end of treatment, body weight and standard length were measured in 30 individuals per aquarium and gonads were examined histologically in 10 individuals of each sex per aquarium. For statistical analysis, the unit of replication was the aquarium, and differences between treatments were considered significant at ␣ Ͻ 0.05 by one-way analysis of variance (ANOVA) and Duncan's multiple-range test. Exposure to 34ЊC reduced oocyte size in ovaries and testicular size (cross-sectional area) and slightly decreased body weight but not standard length. Exposure to 36ЊC significantly reduced ovarian and testicular size, and 52% of females seemed to lack germ cells and may have been sterilized. However, exposure to 36ЊC also greatly reduced body growth and caused spinal curvatures and kidney abnormalities, suggesting that 36ЊC impairs the general health and growth of catfish fry. The results of this study are consistent with the concept that heat treatment can be used to manipulate reproductive development in channel catfish. Further research is needed to establish the appropriate combination of temperature level and treatment duration so as to reduce or eliminate germ cells without adversely affecting somatic growth during the period of treatment.In the United States, the most important farmed fish is the channel catfish Ictalurus punctatus (Hargreaves 2002) and its importance in management as a game species is second only to that of largemouth bass Micropterus salmoides (Siegwarth and Johnson 1998). Commercial fish farmers depend on high fish yields to increase profits, which can offset the cost of production and make fish farming economically viable (Engle and Valderrama 2001). Public fish managers prefer larger fish for stocking in put-and-take waters (public fishing facilities) because fish size is associated with greater angler harvest and increased survivability of the fish after stocking (Shaner and Cook 1996). To meet the needs of the public, hatcheries are required to produce large quantities of fish for stocking, which can result in smaller-than-desired fish size (Engle and Valderrama 2001). Current technologies to enhance somatic growth in fishes require either

High temperature-induced sterility in the female Nile tilapia, Oreochromis niloticus

“…Heat induction of sterility has been reported for some species of fish and other vertebrates (Byerly et al, 2005;Lue et al, 1999a;Strüssmann et al, 1998), but the underlying cellular and molecular mechanisms of heat-induced germ cell loss are not clearly understood. Temperature, an environmental factor, is able to modulate gene expression by epigenetic mechanisms.…”

“…In chicken, heat treatment causes a significant reduction in egg production, egg weight, ovarian weight, and the number of large follicles (Rozenboim et al, 2007). Most scrotal male mammals lose germ cells due to heat stress (Socher et al, 1997), while heat treatment impairs follicular development in female cattle (Wolfenson et al, 1995) and induces germ cell death in some species of fish (Byerly et al, 2005;Ito et al, 2003;Majhi et al, 2009a;Strüssmann et al, 1998).…”

Warm Water Induces Apoptosis, Gonadal Degeneration, and Germ Cell Loss in Subadult PejerreyOdontesthes bonariensis(Pisces, Atheriniformes)

“…This form of germ cell death is associated with various pathological conditions such as cryptorchidism, varicocele, and hydrocele (VanDemark and Free 1970;Harrison 1975;Kandeel and Swerdloff 1988). Heat-induced gonadal degeneration and germ cell loss have been recently reported also in fishes such as pejerrey (Odontesthes bonariensis; Ito et al 2003a), channel catfish (Ictalurus punctatus; Byerly et al 2005), and Florida largemouth bass (Micropterus salmoides floridanus; C. A. Strüssmann and R. Patiño, unpublished observations) and might be widespread in this taxon (reviewed in Strüssmann andPatiño 1995, 1998).…”

“…Thus, the control of this process would facilitate the production of sterile fish, a desirable technology to improve the growth of farmed fish (Hunter and Donaldson 1983;Dunham 1990;Byerly et al 2005) and reduce the ecological impact of exotic species should they escape from captivity. In this context, we designed this experiment to obtain basic information on the cell/tissue dynamics and characteristics of warm water-induced gonadal degeneration and germ cell loss in subadult pejerrey of both sexes and to probe by histochemical and biochemical methods the occurrence of apoptosis during these processes.…”

The effects of temperature and busulfan (Myleran) on the yellowtail tetra Astyanax altiparanae (Pisces, Characiformes) spermatogenesis

“…The present study also showed, for the first time, that high temperature alone can be effective as a sterilization agent in a sexually mature freshwater fish. This was previously shown only for fish incubated at high temperatures from the larval phase or as juveniles [24][25][26][27].…”