RECOVERY OFDURVILLAEA ANTARCTICA(DURVILLEALES) INSIDE AND OUTSIDE LAS CRUCES MARINE RESERVE, CHILE

Abstract

We present the results for over two decades of monitoring on intertidal food-gatherers and the population of the low rocky shore dweller kelp Durvillaea antarctica, a short-distance disperser, inside and outside the no-take marine reserve, Estacion Costera de Investigaciones Marinas (ECIM), at Las Cruces, central Chile. It was hypothesized that protection of an initially extremely depleted population would recover by recolonizing first the no-take area and then adjacent non-protected (exploited) areas. We found that recovery of D. antarctica occurred slowly inside ECIM, with increase in density and biomass, of up to three orders of magnitude as compared to an adjacent non-protected area, which showed approximately 2-yr delay. These results suggest that the kelp population inside ECIM was likely regulated via intraspecific competition, which did not occur outside. Results showed no evidence for juvenile vs. adult density dependence other than a weak relationship for the central area of ECIM. These findings also suggest that the population recovery and cross-boundary seeding subsides affected the population dynamics. Understanding these dynamics may enhance management and conservation policies. Our work highlights the critical value of baseline and long-term comparative studies in marine no-take protected and non-protected areas for understanding how population processes respond to human and conservation practices.

Recovering a lost baseline: missing kelp forests from a metropolitan coast

“…We recognise models of habitat loss that centre on harvesting, where deforestation occurs by direct harvesting of canopies (Castilla et al 2007), or overharvesting of vertebrate predators that triggers an increase in herbivore populations and the overconsumption of algal canopies (Steneck et al 2002). The direct harvesting of seaweeds, however, does not occur on the Adelaide metropolitan coast and is not a model commonly used to explain the widespread and long-term losses observed globally.…”

The social–ecological system framework as a knowledge classificatory system for benthic small-scale fisheries

“…It is well fitted to scientific knowledge (Santelices et al, 1980) that suggests that the period outside the closed season is when the algae grows faster, and therefore one or two harvests can be attained. This harvesting and governance strategy is only possible because the bull-kelp (RU) has a fast yearly growth rate (RU2: Castilla and Bustamante, 1989) and is a small distance disperser (RU3.2: Castilla et al, 2007); thus, the conservation of adult populations has important seeding effects for nearby areas, and seeds do not migrate to distant harbors.…”

Population consequences of biomass loss due to commercial collection of the wild seaweed Postelsia palmaeformis

“…Evidence of the negative effect of commercial take on population dynamics can be found in studies of other large brown, habitat-forming seaweeds such as rockweed Ascophyllum nodosum in the North Atlantic and cochayuyo or bull kelp Durvillaea antarctica in the South Pacific (Keser et al 1981, Lazo & Chapman 1996, Castilla et al 2007). In Chile, D. antarctica has been exploited for human consumption initially by the Mapuches and now by modern intertidal subsistence food-gatherers and artisanal fishers (similar to the history of the Postelsia fishery in northern California; Castilla et al 2007).…”

“…In Chile, D. antarctica has been exploited for human consumption initially by the Mapuches and now by modern intertidal subsistence food-gatherers and artisanal fishers (similar to the history of the Postelsia fishery in northern California; Castilla et al 2007). Creation of a no-take marine reserve in an area that had previously been subject to commercial collection resulted in dramatic increases (~3 orders of magnitude) in plant density and biomass inside the reserve compared to outside, but only after 7 yr of protection (Castilla et al 2007). Increases in abundance of populations adjacent to but outside of the reserve started to occur after about 9 yr, most likely as a result of re-seeding by spores spilling over from inside the reserve.…”