AFSC processed report ; 2007-06

"Walleye pollock Theragra chalcogramma (Pallas) is a commercially important fish species with annual catches in Alaska waters (Gulf of Alaska and Bering Sea) averaging 1.2 million metric tons a year (FAO 2002) worth about US $300 million. There is currently no commercial aquaculture of walleye pollock, but larvae have been successfully reared since the 1980s. Small-scale laboratory rearing has been used to study various aspects of their early life history to better understand conditions that support growth and survival requirements of this species. Factors that are most easily manipulated when rearing fish larvae in the laboratory are light, temperature, and prey type and density. Walleye pollock larvae are visual predators and require a minimum threshold light level to feed (Paul 1983). Recently, many fish have been shown to have ultraviolet-A (320 400 nm, UV-A) sensitive cone pigments in their eyes (Losey et al. 1999). Ability to see in the UV wavelengths may help feeding by providing higher contrast between the background and the prey (Losey et al. 1999). Temperature is an important environmental factor because of its effects on physiological processes in fish. Laboratory studies have shown that prey type can affect growth (Davis and Olla 1992), and prey density can have an effect on the timing of first feeding, the percentage of larvae feeding, and their growth, survival and ingestion rates (PArra and Yufera 2000). This study reports on a series of experiments manipulating light spectrum (the amount of UV light), temperature, prey type and density, first exposure to prey, and turbulence to examine optimal rearing conditions for walleye pollock larvae"--Introduction.

National Marine Fisheries Service (NMFS)