Changes in population parameters and behaviour of blue cod (Parapercis colias; Pinguipedidae) in Long Island—Kokomohua Marine Reserve,Marlborough Sounds,New Zealand

• 1 With the establishment of the 619‐ha Long Island—Kokomohua Marine Reserve in April 1993, a biological monitoring programme designed to investigate changes due to the total no‐take legislation applied to the reserve was initiated.
• 2 Size, distribution and behaviour of blue cod (Parapercis colias; Pinguipedidae) were investigated using baited hooks at reserve and control rubble bottom habitats annually from 1993 to 2000. Blue cod abundance was estimated using visual diver strip transects annually for a period of 9 years from 1992 to 2001.
• 3 A total of 5628 blue cod (2436 reserve and 3192 control specimens) were captured, measured and released. Two years after the reserve was established, the average size of blue cod was 22.4 mm larger inside the reserve compared with control sites outside it.
• 4 Over the duration of the study, the mean length of blue cod captured using baited hooks increased in the no‐take reserve, but declined at the control sites. By the end of the study, in April 2000, the proportion of large blue cod >330 mm in length in the reserve was 35% compared with <1% at the control sites, where recreational fishing activities occurred.
• 5 Blue cod catch rates from experimental fishing in the reserve increased within 11 months of removal of recreational fishing activities and continued to increase up to 47 months, in contrast to the control areas where recreational fishing was permitted, catch rates remained consistently low. Increased catch rates in the reserve were not due to increased blue cod abundance, rather an increase in the proportion of naïve fish in the population.
• 6 From March 1998 to the end of the study, the density of blue cod in the reserve was significantly higher compared with the control sites. This increase was primarily due to an increase in the density of larger blue cod >300 mm length in the reserve and a corresponding small decline in the density of these larger fish at the control sites.
• 7 It is concluded that the cessation of recreational fishing in the reserve had resulted in an increase in blue cod size, catch rate and abundance and also in a change to blue cod behaviour.

Copyright © 2001 John Wiley & Sons, Ltd.