Effects of fishing: effects of fishing resumption on a group of previously protected reefs in the Cairns Section

Abstract

In January 1992 we made baseline surveys of large fishes and other organisms on the five protected MNP B reefs in the Cairns Section that were opened to fishing when the new zoning plan came into effect in April 1992 and on five fished 'control' reefs. The opening reefs were Ribbon #4, Escape, Channel, Wardle and Northeaster, while the appropriate 'controls' were St. Crispins, Ruby, Pell owe, Nathan and Potter. These ten reefs were resurveyed using the same techniques in February 1993, eleven months after the zoning change, to see if we could detect any change on the opened reefs. Surveys were aimed primarily at the large fishes targeted by fishermen, including coral trout, all species of lethrinid (emperors) and all species of lutjanid (snappers). In addition we made surveys of potential prey species (pomacentrids), other important reef organisms (chaetodontids, crown-of-thorns) and encrusting communities (hard coral, soft coral). Underwater visual census techniques were used for the surveys, with 50 x 10 m transects for the large fishes, chaetodontids and crown-of-thorns, and 20 x 2.5 m transects for the small prey fishes. The survey design incorporated three sites on the front of each reef and three on the back, with five replicate transects of each size counted in each site. The surveys on each reef took a day in the field using two observers. The results of the baseline survey have been reported separately (Ayling and Ayling 1992a).