Effects of angling on tunas, sharks, and marlin

Authors: Skomal, G and Chase, B
Meeting: American Fisheries Society Symposium 30
Year: 2002

Many tuna, shark and marlin fall victim to anglers. This causes in these fish:

  • general abnormal physiological function
  • a rise in cortisol, a known indicator of stress
  • acidity of the blood
  • death after release
One of the marlin in this research had the highest level of cortisol ever recorded in a fish.

AMERICAN ANGLERS TARGET LARGE NUMBER OF
TUNA, SHARK, MARLIN

"Large numbers of tunas, sharks, and marlin are released annually by recreational and commercial rod-and-reel fishermen off the east coast of the United States."

SEVERE DISRUPTION OF METABOLISM

"Angling practices result in increased anaerobic activity, muscular fatigue, and time out of water."

"Evidence supports the notion that high anaerobic muscular activity in fish causes extreme homeostatic disruptions that may impede normal physiological and behavioral function and, ultimately, reduce survivorship. Since blood reflects changes in muscle biochemistry, these perturbations can be measured and quantified."

"To quantify the physiological consequences of high anaerobic muscular exercise, blood was sampled from 312 fish comprising 12 species of tunas (230), sharks (77), and marlin (5), after exposure to rod-and-reel angling."

STRESS AT EXTREME LEVEL

marlin-angling-cruelty.jpg

"The primary response to stress included a significant elevation of blood cortisol in bluefin tuna, yellow fin tuna, and white marlin. In the tunas, a significant increase occurred 10 minutes into the angling event."

"Cortisol levels measured in the white marlin were among the highest reported for any fish."

TUNA HUNTED TO DEATH

"A single bluefin tuna angled for 42 minutes died immediately after release. This fish had a depressed blood pH and high blood lactate levels indicative of a severe acidemia¹."

¹acidemia - where the acidity of the blood is much higher than is usual and desirable

Fish Pain