Depth and mortality

Authors: Muoneke, Maurice and Childress, W. Michael
Journal: Reviews in Fisheries Science, 2(2): 123-156
Year: 1994
Where: Texas A&M University, and, Texas Parks and Wildlife Department

This review paper found that a significant number of fish die when caught at depth - the deeper the water, the more deaths that follow.

Rainbow trout
depth mortality
1 to 3 metres 10% to 33%
6 metres 50% to 70%

Black crappie
depth mortality
6 metres 19%
16 metres 77%

Blue rockfish, caught at 76 metres by anglers, caused the fish’s eyes to come out of their sockets by gases that expand inside the fish’s head as it is brought to the surface.


bluerockfish angling cruelty

Anglers who think that they are doing the fish a favour by inserting a pin, or other sharp object, into the suffering fish’s eye, actually increases the chance of the fish dying. However, such barbaric treatment may help the angler get rid of their spoils as the fish drops from the surface.

RAINBOW TROUT - THIRD DIE WHEN CAUGHT AT 1 TO 3 METERS
- HALF DIE WHEN CAUGHT AT 6 METERS

"Faccin (1983) reported that the mortality of rainbow trout ranged from 10 to 33% among fish confined at depths of 1 to 3 m compared to 50 to 70% among fish restrained at 6 m."

BLACK CRAPPIE - UP TO THREE-QUARTERS
DIE WHEN CAUGHT AT 6 TO 16 METERS

"Childress (1989) observed mortalities of 19 and 77% for black crappie caught from depths of 6 and 16 m, respectively."

BLUE ROCKFISH CAUGHT AT 76 METERS
- EYES FORCED OUT OF SOCKETS

"Gotshall (1964) reported that blue rockfish brought from depths of 76.2 m suffered from a "popeye" condition, in which gases in the skull expanded and forced the eyes out of their sockets. Insertion of a sharp object into the eye cavity at the juncture of the prefrontal and lacrimal bones usually relieved the condition, but caused greater mortality than nondeflation."
Childress, V. M (1989), Catch-and-release mortality of white and black crappie. In: Catcb-and-Release Fishing— A Decade of Experience, pp. 175-186. (Barnhart, R. A. and T. D. Roelofs, Eds.). Arcata, CA: Humboldt State University, California Cooperative Fisheries Research Unit.
Faccin, A (1983), Hooking mortality of fly-caught Duncan River rainbow trout (Salmo gairdneri) in Harper Lake, British Columbia. Fish. Tech. Circ. 58. British Columbia Fish and Wildlife.
Gotshall, D. (1964), Increasing tagged rockfish (Genus Sebastodes) survival by deflating the swim bladder. Calif. Fish Game, 50:253-260.
Fish Pain