The influence of protection and temperature on subtropical reef fish assemblages in Cape Byron Marine Park

Abstract

Abstract Diver‐held video transect surveys at a subtropical reef complex in eastern Australia documented a significant difference in the fish assemblages eight years after the area was closed to fishing. Average sea temperatures at depth were 1–3°C warmer during the second survey period, and autumn averaged 5–6°C warmer than spring. Large differences in fish assemblages between the seasons in 2006 were not observed in subsequent 2014 surveys. Rather than any general shift towards greater topicalisation of the assemblage in warmer conditions, the difference between the assemblage sampled in the coldest sample period and the three warmer periods was a lower frequency of occurrence of both tropical and non-tropical species and decreased asymptotic species richness. Species that were otherwise rare, which consisted of a higher proportion of tropical species, were more likely to be absent in colder conditions. This was particularly so at the deepest and coldest location. Therefore, in this region warmer waters tend to increase the richness and abundance of most fish, but particularly rare tropical species. Protection from fishing since 2005 also contributed to the inter‐year differences with increased abundance of most fishery‐targeted species regardless of climatic affinities in 2014.