Abstract:a b s t r a c tThe Peruvian Bay scallop (Argopecten purpuratus) fishery in Independencia bay (Southern Peru) is being subjected to great inter-annual variability in catch and effort. This is mainly due to the ENSO (El Niño-Southern oscillation)-caused changes in the population dynamics of the stock, which greatly proliferated during the El Niño events 1983 and 1998. As a consequence "gold rush" conditions arose and resource users profited from a multi-million dollar export business. After the El Niño booms, th… Show more
“…Based on the model, recruitment and production increases of scallops account for this result, as scallops consume 58% of phytoplankton production during EN. Wolff et al (2007) found that the increase in scallops was likely a non-trophic effect resulting from increased larval survival in warmer temperatures. This recruitment success combined with increased oxygen concentrations is likely the main cause of the increase in fisheries yield.…”
Section: Summary Statistics Flow Structure and Maturitymentioning
“…Based on the model, recruitment and production increases of scallops account for this result, as scallops consume 58% of phytoplankton production during EN. Wolff et al (2007) found that the increase in scallops was likely a non-trophic effect resulting from increased larval survival in warmer temperatures. This recruitment success combined with increased oxygen concentrations is likely the main cause of the increase in fisheries yield.…”
Section: Summary Statistics Flow Structure and Maturitymentioning
“…When SS and SF were applied together, as done by Wolff et al (2007) for Independence Bay, the regression was not significant (R 2 = 0.362; P = 0.509). The addition of the independent variable RD increased the fit dramatically (R 2 = 0.959; P = 0.060); however, a significant regression was achieved only from the combination of the independent variables SS and RD (without SF) (R 2 = 0.916; P = 0.024*).…”
Section: Multiple Regressionmentioning
confidence: 99%
“…These events improve benthic oxygen concentrations through a lowering of the thermocline and also increased metabolic activity (respiration, somatic growth) in response to the increased temperature. New findings suggest that reduced mortality in the larval stage, due to faster development to settlement times, may be mainly responsible for population booms during EN periods (Wolff et al 2007). Our exploration of the environmental influences on the scallop stock in Sechura Bay suggests a greater importance of riverine inputs to the bay.…”
Section: Importance Of Environmental Variability and Implications Formentioning
confidence: 99%
“…These drivers are well cited in the literature as having significant environmental influences on their dynamics. Populations of the scallop A. purpuratus in Independence Bay have been shown to fluctuate more in response to temperature-mediated larval development time and subsequent mortality changes rather than from purely trophic changes (Wolff et al 2007;Taylor et al 2007d). Penaeid shrimp dynamics in the region have been correlated to shifts in carrying capacity as a result of variable SST and river discharge (Mendo and Tam 1993).…”
Section: Simulations Of Temporal Dynamicsmentioning
confidence: 99%
“…Using the methods employed by Wolff et al (2007) for the scallop stocks in Independence Bay, Peru (16°S), the model attempts to forecast scallop catch as a function of the environmental conditions during the previous spawning period. Specifically, the dependent variable was defined as the scallop 'catch' (kg), versus the independent variables 'spawning stock' (kg) and the temperature-dependent 'settlement factor' (arbitrary units) for scallop recruitment.…”
Section: Simulations Of Temporal Dynamicsmentioning
Interannual environmental variability in Peru is dominated by the El Niño Southern Oscillation (ENSO). The most dramatic changes are associated with the warm El Niño (EN) phase (opposite the cold La Niña phase), which disrupts the normal coastal upwelling and affects the dynamics of many coastal marine and terrestrial resources. This study presents a trophic model for Sechura Bay, located at the northern extension of the Peruvian upwelling system, where ENSO-induced environmental variability is most extreme. Using an initial steady-state model for the year 1996, we explore the dynamics of the ecosystem through the year 2003 (including the strong EN of 1997/98 and the weaker EN of 2002/03). Based on support from literature, we force biomass of several non-trophicallymediated 'drivers' (e.g. Scallops, Benthic detritivores, Octopus, and Littoral fish) to observe whether the fit between historical and simulated changes (by the trophic model) is improved. The results indicate that the Sechura Bay Ecosystem is a relatively inefficient system from a community energetics point of view, likely due to the periodic perturbations of ENSO. A combination of high system productivity and low trophic level target species of invertebrates (i.e. scallops) and fish (i.e. anchoveta) results in high catches and an efficient fishery. The importance of environmental drivers is suggested, given the relatively small improvements in the fit of the simulation with the addition of trophic drivers on remaining functional groups' dynamics. An additional multivariate regression model is presented for the scallop Argopecten purpuratus, which demonstrates a significant correlation between both spawning stock size and riverine discharge-mediated mortality on catch levels. These results are discussed in the context of the appropriateness of trophodynamic modeling in relatively open systems, and how management strategies may be focused given the highly environmentally influenced marine resources of the region.
‘La Rinconada Marine’ Reserve (MR), Chile was created in 1997 to preserve the genetic stock of the scallop Argopecten purpuratus and eventually to supply seed to areas outside of the reserve and support aquaculture activities. Data from biological and fisheries monitoring of A. purpuratus as well as environmental conditions in the MR are available for the period from 1993 to 2009.
The continuous extraction of A. purpuratus from La Rinconada MR in Chile, without a science‐based exploitation plan, has not only decreased the abundance and population structure of the species but has also significantly affected seed settlement in artificial collectors and population recruitment. Therefore, the goals of the MR have not been achieved.
This review of biological and fishing studies of A. purpuratus in La Rinconada MR provides a basis for the implementation of a sustainable programme for the natural collection of A. purpuratus seed for population recovery.
A. purpuratus recruitment varies substantially between years and is not strongly related to the size of the parental population. Larval collection and recruitment depend on environmental events (El Niño‐Southern Oscillation) and biological substrate availability (Rhodymenia red algae). These factors produce a bentho‐pelagic decoupling between parental abundance, larval production and subsequent recruitment of A. purpuratus that limits stock recovery in the MR.
To address the poor population status of A. purpuratus in the MR, recovery of the adult population is needed. Therefore, an assisted collection and recruitment strategy is proposed to increase the population and enable the generation of surplus seed, fulfilling the initial aims of La Rinconada MR.
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