Trajectories of spiny lobster Jasus edwardsii recovery in New Zealand marine reserves: is settlement a driver?

Abstract

Monitoring species' response in marine protected areas is important for informing both the management of those areas and the establishment of additional protected areas. Populations of spiny lobsters Jasus edwardsii were monitored in eight New Zealand marine reserves for up to 34 years. The populations displayed highly variable responses to protection. While a few showed rapid (within 1-2 years of protection) increases in abundance, others showed little response even after a decade of protection. Some reserves displayed little initial recovery, then a sudden increase following several years of protection, while others displayed significant declines in abundance following initial recovery. Marine reserves located in areas with initially high densities of juveniles tended to have rapid recovery, but aspects of reserve design had no significant influence on the recovery rate. Variability among recovery trajectories also suggests that supply-side dynamics may be a key driver of lobster recovery. Densities of legal-sized lobsters were positively correlated with reserve age, but the abundance of juvenile lobsters increased in all but one reserve, indicating enhanced recruitment, survival and/or movement of juvenile lobsters into reserves. It is important to consider the placement of reserves, with respect to potential levels of larval supply, when establishing marine reserves for either conservation or fisheries management purposes and for evaluating their effectiveness.

Effects of marine reserves in the context of spatial and temporal variation: an analysis using Bayesian zero-inflated mixed models

“…Our results indicated large differences in the effects of reserves on legal snapper among locations, which were not reported by Willis et al (2003a). Differences in reserve effects have also been observed in a recent study of another species (rock lobster Jasus edwardsii) in a set of reserves which included the three studied here (Freeman et al 2012). The largest effect for legal snapper was observed at Leigh, with densities estimated to be nearly 20 times greater within the reserve than outside the reserve, while Tawharanui and Hahei had effect sizes of 8 and 16, respectively.…”

“…Legal snapper in the Hahei reserve had a mean density similar to that of the Tawharanui reserve, despite this location having much lower densities of sublegal snapper and legal snapper outside the reserve, consistent with the general southward decrease in the abundance of this species. This could be due to the reserve at Hahei being much larger than the other two and, perhaps more importantly (Freeman et al 2012), having more than twice the offshore extent (Table 1). These patterns are consistent with the hypothesis that the size of the reserves plays a key role in producing the observed variation in their effects.…”

“…The position of reserves with respect to patterns of onshore migration in this species is therefore likely to be an important factor in determining their success. Patterns of settlement of larvae in the vicinity of reserves could also potentially influence densities of sublegal-and legal-sized snapper in reserves, but post-settlement processes such as mortality and dispersal are likely to moderate the influence of larval supply on adult densities (Freeman et al 2012). The colonisation of reserves by seasonal migrants potentially allows the number of resident adult snapper to accumulate more rapidly than would be possible through the progression of juvenile fish to adulthood (as documented at the nearby Poor Knights Islands Marine Reserve by Denny et al 2004), provided the reserve is large enough to protect them once they are resident.…”

First quantification of subtidal community structure at Tristan da Cunha Islands in the remote South Atlantic: from kelp forests to the deep sea

“…Despite being fished at Tristan da Cunha, lobster abundances there are comparable to densities of lobsters in protected areas in other parts of the world. For example, mean densities of the spiny lobster, Panulirus cygnus , in protected areas in Rottnest Island, West Australia were 7.08 lobsters per 100 m 2 (compared to 0.2 per 100 m 2 in fished areas) [ 49 ] and the highest densities of Jasus edwardsii in multiple protected areas across New Zealand were 6 and 12 lobsters per 100 m 2 in two MPAs that were protected for roughly 15 years [ 50 ]. While lobster densities and biomass at Tristan da Cunha differed little among islands, there were some important within-island variability.…”

The Ecological and Evolutionary Consequences of Marine Reserves

“…Environmentally driven stochastic recruitment can interact with these transient responses to further increase the amount of variability and time to longer-term increases (particularly for populations with intermediate age at maturity; see White et al 2013, White & Rogers-Bennett 2010. Empirical observations include such variation in initial population response to reserve establishment (e.g., Freeman et al 2012). Another possible source of population decline after reserve establishment is increased parasite or disease prevalence associated with increased population density, depending on the drivers of disease susceptibility and transmission ( Table 1).…”