Blue cod

Abstract: Estimates of the relative density of fishes form the basis of many marine ecological studies as well as the assessment of effects of fishing or pollution Plasticity in the behavioural response of large reef fishes to SCUBA divers means that commonly used underwater visual census (UVC) techniques do not always provide reliable estimates of relative density The paper describes the system configuration, deployment methods, testing and use of a remotely deployed baited underwater video (BUV) system for the survey of carnivorous reef fishes (snapper, Pagrus auratus and blue cod,Parapercis colias) in marine reserves of northern New Zealand Concurrent UVC and BUV surveys inside and outside a marine reserve showed that, whereas UVC detected few snapper in either area (resulting in little confidence in statistically significant results), BUV demonstrated significant differences in relative density Conversely, blue cod were found to occur at significantly higher densities within the reserve by UVC, but not by BUV The provision of accurate estimates of fish size (<20 mm error) from video footage also illustrated differences in size structure between protected and fished populations The data suggest that a combination of survey techniques is likely to be necessary where multispecies assemblages are being assessed

Abstract: The possible effects that marine reserve protection has had on densities of some reef fish and large invertebrates were investigated near Leigh (north‐eastern New Zealand) by a series of sampling programmes between 1976 and 1988. Fish counts at intervals during the 6 years after the initial establishment of the Cape Rodney to Okakari Point Marine Reserve in 1975 suggested that red moki (Cheilodactylus spectabilis) had increased in abundance whereas five others had remained at approximately constant densities. A comparison of data between 1978 and 1988 also revealed few consistent differences in fish abundances. A detailed survey in 1988 between sites inside and outside the marine reserve showed no clear patterns for sea urchins (Evechinus chloroticus) and several fish; trends for increased abundances in the marine reserve of fish such as snapper Pagrus (=Chrysophrys) auratus, blue cod (Parapercis colias), and red moki; a very striking increase in numbers of rock lobsters (Jasus edwardsii) within ...

Abstract: 1. Spillover of organisms from marine reserves may augment adjacent areas, and is often cited as an important reason for the establishment of marine protected areas. Spillover is dependent on residence or limited dispersal of organisms resulting in an increase in their abundance and size within a marine reserve. 2. To investigate movement (i.e. spillover versus residence) we tagged and released 90 blue cod Parapercis colias (Pinguipedidae) at each of four sites, two in and two adjacent to Long Island–Kokomohua Marine Reserve, Marlborough Sounds, New Zealand. The study was done 4–5 years after establishment of the no-take reserve. 3. Abundances of blue cod were similar in and out of the marine reserve, but mean estimated size was 4 cm larger in the reserve than at fished sites. 4. Fewer tag resights were made in the reserve than at fished sites, and tagged blue cod were resighted at greater depths in the reserve than at fished sites. 5. Most resights (75% for fished sites, 73% for reserve sites) were made within 100 m of the tagging sites, and the number of resights declined through time, though tagged individuals were resighted up to 31 months after tagging. 6. The lower number of tag resights at reserve sites, despite the lack of extraction, is consistent with some blue cod at reserve sites moving longer distances than those at fished sites. 7. The greater size of individuals in the reserve and limited dispersal of a proportion of the population show that survivorship of blue cod is increased within marine reserves. 8. Computer simulations based on measured dispersals indicate that even marine reserves of a few hundred metres long-shore extent have the potential to supplement fished populations nearby. 9. These data provide direct evidence of limited dispersal of the most common edible reef fish in the Marlborough Sounds. Blue cod will grow to larger sizes in marine reserves and via spillover will become available to fishers in adjacent areas of contiguous coast. Copyright © 2000 John Wiley & Sons, Ltd.

Abstract: Size and abundance data were compiled and collated for blue cod Parapercis colias and rock lobster Jasus edwardsii from New Zealand marine reserve (MR) studies for a meta-analysis to test the null hypotheses that reserve status does not affect the size or abundance of either species. Calculation of meta-analysis effect sizes revealed that significant differences in effect size existed among studies, meaning that the biological response to MR status of both species in terms of their changes in size and/or abundance differed significantly among the MRs. Analysis revealed that blue cod were bigger inside compared with outside MRs in 9 of 10 studies and were more abundant inside MRs in 8 of 11 studies, and that rock lobster were bigger inside the MRs in 12 of 13 studies and more abundant inside the MRs in 11 of 14 studies. These findings indicate that MR protection can result in more and bigger individuals soon after the establishment of the MR (mean of 6.5 yr for blue cod, 8.5 yr for rock lobster) despite small sample sizes of studies (≤10 for blue cod, ≤14 for rock lobster). Focused comparison tests did not reveal any relationship between rock lobster or blue cod size or abundance and either age or area of MRs. Our results demonstrate that no-take MRs are valuable conservation tools for species such as blue cod and rock lobster (and probably also for other exploited species with similar life history characteristics and habitat requirements) and that statistically detectable conser- vation benefits are apparent after only a few years of protection.