Distribution patters of planktivorous reef fish along the coast of northeastern New Zealand

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Abstract
Broad-scale distribution patterns of planktivorous reef fish were described using visual counts along 100 km of the coast of Northland. New Zealand; including sampling at islands across the continental shelf. Temporal variation in abundance was examined also. Comparisons between strip transects and rapid visual counts (RVC''s) indicated the RVC''s were most appropriate for a broad-scale survey. Different abundance patterns were found for 13 species of planktivorous fish. Some species exhibited significant differences across the shelf (e.g. Chromis dispilus and Scorpis aequipinnis). No cross-shelf differences were detected for others (e.g. Casioperca lepidoptera and Pseudocaranx dentex). Abundance of 2 species differed along a north-south axis. The proportional representation of species varied within the study area. C. dispilus dominated over a large part of the study area. The southwestern region had a high proportion of S. aequipinnis and/or Trachurus novaezelandiae. Over 5 yr the composition of fish at an outer-shelf and inner-shelf location remained similar. Two groups of planktivorous fish were identified, those with a close association (e.g. C. dispilus) and those which a temporary association with reefs (e.g. Trachurus novaezealandiae). The first group showed little variation in abundance at 2 sites over 15 mo, while the other exhibited considerable temporal variation. Regular variation in abundance at different times of the day was not found for either group. It is suggested that hydrology may influence the composition and abundance of zooplankton which may influence survivorship of presettlement reef fish and the feeding of fish on reefs. Investigation of proximate factors which may determine the distribution patterns of planktivorous fish is required.