Spectral sensitivity of the cod,Gadus morhuaL.

Abstract

The spectral sensitivity of the cod was determined under both dark adapted and light adapted conditions in the laboratory. Cod were trained by cardiac conditioning to detect a difference in radiance between an image of spots and the background radiance of a screen. Thresholds for this response were measured for a range of different wavelengths, and expressed as quantum adjusted values. Electroretinographic studies were also performed on the eyes of cod, and spectral sensitivity curves prepared. Under dark adapted conditions both the behavioural and e.r.g. derived curves showed greatest sensitivity in the blue/green at 490 nm, matching the absorption curve for rhodopsin. A secondary peak in the behaviourally derived curve in the green/yellow at 550 nm indicated that a population of yellow cones may be implicated with the rods in scotopic vision. Under light adapted conditions the behavioural curves showed a shift to the blue, perhaps indicating an adaption to the high red content of the illuminating source. The e.r.g. curve showed greatest sensitivity to blue/green, as in the scotopic experiments but with an enhanced response at 550 nm, indicating greater cone activity. It is suggested that there is complex interaction between rods and cones in the cod retina, both types of receptor being active over a wide range of light intensities.

Combination of a sorting grid and a square mesh panel to optimize size selection in the North-East Arctic cod (Gadus morhua) and redfish (Sebastes spp.) trawl fisheries

“…Red light was chosen because it is thought to affect fish behavior less than more-traditionally used white light (Anthony and Hawkins, 1983). The camera was protected by a stainless-steel housing with a depth limit of 300 m.…”

Improving release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in the Barents Sea demersal trawl fishery by stimulating escape behaviour

“…Otherwise, to provide appropriate illumination, we used a Metalsub FL 1255 halogen lamp (1500 lm and 3200 K) connected to a Metalsub FX 1209 Dual battery pack (http://www.metalsub.nl/). A piece of red plastic film was fixed to the halogen lamp to turn the white light to red light to reduce the impact of artificial light on fish behaviour (Anthony and Hawkins 1983). The camera was attached to the top panel of the square mesh section facing backwards towards the stimulation devices.…”

Escape responses in juvenile Atlantic cod Gadus morhua L.: the effects of turbidity and predator speed

“…Anthony, 1981;Anthony and Hawkins, 1983). Understanding how turbidity influences predator evasion by juvenile cod will also aid in predicting the impact of increases in turbidity from human activities (Bonsdorff et al, 1997;Frid et al, 2003) on its vulnerability to predation.…”