Empirical Before-After Control-Impact Study Shows Positive Effects of Small-Scale Marine Protected Areas on Northern Cod and Lobster

Despite the fact that marine protected areas (MPAs) are increasing used as tools in fisheries management and conservation, examples of replicated experiments that sampled organismal density before and after establishment of MPAs at sites both inside and outside of the MPAs are rare. Because the implementation of MPAs can be perceived as an opportunity cost to certain stakeholder groups such as commercial and recreational fishers, there is a need for science-based assessments of these areas.  Also, while MPAs with potential to protect temperate species throughout their life histories will need to be large in more open systems, it is not known whether small-scale MPAs may confer benefits to demersal species with pelagic larval stages along convoluted coastlines in high latitudes. Moland et al. (2013) present one of the northernmost documentations of small-scale MPA effects demonstrated by a replicated before-after control-impact (BACI) approach. Only a few studies have previously used this recommended design and none in northern temperate coastal regions. Moland et al. show that both lobster and cod generally responded positively to protection, but also that there were clear regional differences in MPA responses and population developments in adjacent fished areas.Evelyn Byer
                  Moland, E., Olsen, E. M., Knutsen, H., Garrigou, P., Espeland, S. H., Kleiven A. R., Andre, C., Knutsen J., A., 2013. Lobster and Cod Benefit From Small-Scale Northern Marine Protected Areas: Inference From an Empirical Before-After Control-Impact Study. Proc R Soc B 280: 20122679.

                  Moland and colleagues in Norway, Sweden, and France applied a BACI study design to assess the effect of MPAs on lobster and cod in a northern temperate marine ecosystem. Their study encompassed two organisms: the European lobster, and the Atlantic cod. They studied these organisms because catch rates of European lobster has decreased by 65 per cent from the 1950s to 2000s in Norway. Also, a recent study found that 50 per cent of potentially mature cod were removed by fishing each year, suggesting a high level of fishing pressure. Moland et al. established MPAs along the Norwegian Skagerrak coast to generate knowledge on the development of lobster population in areas unaffected by extractive fishing. Capture of lobster was banned in the MPAs from September 2006, with only hook and line fishing allowed. The MPAs were located in Fodevigen, Bolaerve archipelago, and Kvernakjaer. Control areas were separated from MPAs by distances of 1700, 850, and 2250 meters, respectively. At each location, MPAs and control areas are of approximately equal size. Lobsters were sampled using an annual standardized research trapping survey, including capture-mark-recapture, during three consecutive years prior to protection. In 2006, adjacent control areas were designated and included in the survey. Lobsters were sampled using standard ‘parlour’ traps deployed in 1030 meters depth. A set of 25 traps fished for four days within each control group and MPA every year. Lobsters were measured and tagged immediately upon capture and released at the same site. An independent study on cod was conducted in the same area during 20052010 and was included in this study. Cod were sampled in the Flodevigen MPA, Arendal, Lillesand, and Risor using fyke nets in shallow water. Sampling efforts ranged from 74411 trap hauls among years and sites. Individual cods were measured to the nearest cm, tagged, and released at the site of capture. Data analyses and plotting of results for lobster were conducted using R software. Moland et al. analyzed spatial and temporal variation in lobster catch per unit effort (CPUE) and size. They used a zero-inflated Poisson regression model to analyze the effects of year, treatment, and region on CPUE. The Vuong test was used to test whether the zero-inflated model was a significant improvement over a standard Poisson model. The body size data was analyzed using analysis of variance (ANOVA). Spatial and temporal variation in cod catch and cod size was analyzed using generalized linear models.
2074 and 1681 lobsters were captured, measured, and tagged in the MPAs and control areas respectively. The Flodevigen MPA had a modest increase in CPUE, evident in year two of protection and onwards, whereas the rate of change in the control area was negligible. CPUE was similar in the Bolaerne MPA and control area before MPA designation, with increasing difference in all years after designation. At Kvernskjaer, CPUE in the MPA increased rapidly with a mean that was more or less equal to the control area in 2007. The mean relative CPUE increased by 245 per cent in MPAs, whereas mean relative CPUE in control areas increased by 87 per cent. Mean body size of lobster increased by 13.0 per cent and 2.6 per cent in MPAs and control areas, respectively. On the other hand, 12,116 cod were captured and measured. Prior to designation of MPAs, cod from the MPA were, on average, among the smallest in the study. From 2008 and onwards, the MPA cod had the highest average size. These general study differences demonstrate spatial heterogeneity in effects of protection in largely similar systems that cannot be given a straightforward explanation. Moland et al. conclude that harvested marine species in northern temperate waters may benefit from small-scale MPAs, and emphasize the need for replicated MPA/control area pairs in the assessment of MPAs, as monitoring single MPAs may lead to variable conclusions.

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