Survival experiments of undersized cod in a hand-line fishery at Iceland

• Main Authors: Ólafur K Pálsson, Haraldur A Einarsson, Höskuldur Björnsson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2003
• Subjects: Gadus morhua; Iceland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1041.2584; http://www.hafro.is/Bokasafn/Greinar/fish_res_61-73.pdf

Abstract Eight survival experiments, including two controls, were carried out to analyse mortality of undersized cod (Gadus morhua L) discarded in the hand-line fishery north of Iceland. The fish were held in eight cylindrical cages over a period of 4-9 days and inspected regularly. All fish were checked for injuries. The data were analysed using generalized linear models (GLMs) in Splus. Multiple injuries were significantly more frequent in deep water than in shallow water. The reverse was the case for single injuries. The most common injuries were to the jaws, the tongue and the vomer, followed by injuries near eyes and on cheeks. No mortality was observed in the control experiments. Overall, mortality rate in four valid experiments was 43%, but significantly higher in deep water (54%) than in shallow water (32%). A significant decrease in mortality was found with increasing fish length. Fish with a single injury had significantly lower mortality rate (27%) than fish with multiple (more than one) injuries (59%). A GLM analysis of mortalities as a function of type of injuries indicates four categories of injuries with respect to level of mortality. It is concluded, that high frequency of multiple injuries in deep water and high mortality rate of multiple-injured fish are the main explanations of higher mortality rate in deep water than in shallow water.