Chapter 13: Catfishes (Siluriformes)
Catfishes are found on all the continents except Antarctica, with more than 3,000 described species. In this chapter, hatchery techniques for three groups of the most widely cultured catfishes representing different modes of reproduction and culture are discussed.
Channel Catfish is an important food and sport species in the family Ictaluridae, native to North America. It was first propagated under hatchery conditions in 1916. Its basic cultural techniques were developed at public fish hatcheries in the mid-west from 1925 to 1950. By the mid-1950s hatchery techniques and food fish production procedures were established enough to support the growth of a commercial industry. Channel Catfish has since become the most widely produced warmwater food fish in the USA. It has been introduced into over 40 countries.
Channel Catfish are a relatively long-lived species that may attain a maximum size of more than 27 kg under natural conditions, and an age of >20 years. When cultured they can grow to 20 to 25 cm in the first 4 to 5 months after hatching. A market size fish of 340 to 680 g can be produced within two years after hatching. Channel Catfish can reach sexual maturity at an age of 2 years when growth conditions are favorable. This is especially true of males. However, 3-year old fish are preferred as first time spawners if dependable spawning is to be obtained. Females continue to produce eggs for a number of years with gravid 20 kg individuals being occasionally encountered in wild populations. Females at sexual maturity can be expected to weigh 1.3 kg while males of the same age will usually be slightly larger at 1.3 to 1.5 kg.
As the spawning season approaches, sexual dimorphism is apparent in mature fish. Males have a broader and more muscular head than the females (Figure 13.1.1). Pigmentation of males tends to be darker especially as the fish age. The genital orifice of the male is small in diameter and located at the tip of the genital papilla. The papilla is easily seen in mature males (Figure 13.1.2). The villiform nature of the testes does not present enough tissue mass to allow sperm to be released when the abdomen is squeezed. As such, mature males cannot be identified based on whether or not semen is released when the abdominal area of the fish is squeezed.