Changes in community structure in temperate marine reserves

Abstract

ABSTRACT. 'No-take' marine reserves provide a valuable tool for managing marine resources as well as for providing relatively undisturbed habitat with which to assess modifications to ecosystems. We studied 2 marine reserves in northeastern New Zealand, the Leigh Marine Reserve (established 1975) and Tawharanui Marine Park (established 1982) in order to assess whether changes in protected predator populations had resulted in other indirect changes to grazers and consequently to algal abundance. Estimates of abundance of the most common demersal predatory fish Pagrus auratus indicated that adults of this species (i.e. large enough to prey upon urchins) were at least 5.75 and 8.70 times more abundant inside reserves than in adjacent unprotected areas. Overall, P auratus were also much larger inside reserves with mean total lengths of 316 mm compared with 186 mm in fished areas. The spiny lobster Jasus edwardsii displayed similar trends, and was approximately 1.6 to 3.7 times more abundant inside the reserves than outside. Lobsters within the reserves had a mean carapace length of 109.9 mm, compared with 93.5 mm outside the reserves. In one of the reserves, densities of the sea urchin Evechinus chloroticus had declined from 4.9 to 1.4 m-2 since 1978 in areas formerly dominated by it. Consequently, kelp forests were more extensive in 1998 than they were at the time of reserve creation. Urchin-dominated barrens occupied only 14 % of available reef substratum in reserves as opposed to 40"4 in unprotected areas. These changes in community structure, which have persisted since at least 1994, demonstrate not only higher trophic complexity than anticipated in Australasian ecosystems but also increased primary and secondary productivity in marine reserves as a consequence of protection. Trends inside reserves indicate large-scale reduction of benthic primary production as an indirect result of fishing activity in unprotected areas.

Quantitative characterisation of reef fish diversity among nearshore habitats in a northeastern New Zealand marine reserve

“…taxonomic measurements of diversity suggested sponge flats were more diverse than traditional indices (S, H', l-X, Nl, N2) would otherwise infer. Previous studies have shown that differences in diversity between habitats could be owing to varying levels of structural complexity (Mora et al 2003;Anderson & Millar 2004) and productivity (Taylor 1998;Babcock et al 1999), although these factors were not quantified in the present study.…”

Decadal trends in marine reserves reveal differential rates of change in direct and indirect effects

“…For example Heliocidaris erythrogramma at Maria Island is characteristically cryptic, remaining in crevices or burrows, rarely venturing out to feed, and surviving on drift algae (30). In northeastern New Zealand, the urchin Evechinus chloroticus is often conspicuous at depths between 6-12 m and creates barren grounds by openly grazing on kelp forests (11). However, in reserves Evechinus changes its behavior, becoming cryptic (13) and surviving on drift algae (31), most likely a response to increased densities of predators, as has been experimentally confirmed in other urchins (32).…”

“…The few changes observed in populations of nontargeted species in reserves are thought to result from indirect effects that develop after the restoration of populations of higher predators (11)(12)(13)(14). For example, in tropical systems, the recovery of herbivorous fish in reserves can lead to a decrease in macroalgal biomass and the release of space, resulting in enhanced recruitment of corals (15).…”

“…For example, in tropical systems, the recovery of herbivorous fish in reserves can lead to a decrease in macroalgal biomass and the release of space, resulting in enhanced recruitment of corals (15). In temperate reef ecosystems, the recovery of lobsters and large fish in marine reserves in New Zealand has led to higher predation and the decline of sea urchin populations, and in turn a reduction of grazing and the recovery of kelp forests (11,13). Indirect trophic interactions resulting from changes at trophic levels two or more trophic levels higher are often termed trophic cascades (16).…”

Evaluating the effect of fishery closures: Lessons learnt from the Plaice Box

“…This stems from their relative simplicity, ease of enforcement and intuitive logic. The perceived failures of traditional methods of fisheries management worldwide with declining stocks, overfishing, and general fleet overcapacity (Worm et al 2009, Pauly et al 2002 have also contributed to the clamor for Marine Protected Areas to be set up (Sumaila et al 2000, Kaiser 2005, Laurel and Bradbury 2006, Babcock et al 1999. Furthermore some recent studies have shown that, in comparison with other human maritime activities, (e.g.…”