Effects of marine protected areas on fish communities in a hotspot of climate change and invasion

Abstract

The positive ecological effect of fully protected Marine Protected Areas (MPAs) on fish populations has been widely explored. Key indicators of fully protected MPAs effectiveness include an increase in biomass, density, and body size of commercially exploited large fishes. Fully protected MPAs are also hypothesized to be more resilient to both marine invasions and ocean warming, but this has seldom been tested. The eastern Mediterranean (Levantine) basin is the warmest region in the Mediterranean. Moreover, this region is the front-line of biological invasion from the Red Sea via the Suez Canal. Thus, MPAs in this region are faced with both high numbers of exotic species and warm temperatures. Assessing the performance of MPAs in this region is important for understanding their effectiveness under adverse future conditions worldwide. The ecological effectiveness of four MPAs along the Levantine Israeli coast was followed along over five years and compared with adjacent fished control area. Sampling was conducted in both old (>20 years of enforcement) and young MPAs, which only recently became fully protected. Using SCUBA diving surveys, 978 visual transects were performed to assess fish abundance, size, and diversity. We found clear indications for the benefits of the MPAs as evident by higher numbers of large fishes and groupers within protected areas. In the largest and oldest MPA we also found higher total and commercial fish biomass. In addition, we show a clear increase in the number of groupers over time, both within and outside MPAs, that may be associated with increased fishing regulation and enforcement. We found no clear evidence for a lower number of exotic species within MPAs. Our findings suggest that restrictions on recreational and commercial fishing within MPAs benefit the recovery of fish populations even in warm waters and when faced with marine invasions, and that the effectiveness of MPAs may be evident after only a few years of protection.

Evaluation of fisheries management policies in the alien species-rich Eastern Mediterranean under climate change

“…These results are in line with the results of the abovementioned surveys (NPA, 2015) and other studies in the Mediterranean (D'Amen and Azzurro, 2019) and in Israel in places where there is continuous monitoring of protected areas compared to what happens outside the protected area (such as the Achziv reserve in the northern part of the territorial waters in Israel). It seems that there is an increase in the amount of local species inside the reserve compared to the area outside (Frid et al, 2022). This observation also indirectly verifies the model.…”

An invasive herbivorous fish (Siganus rivulatus) influences both benthic and planktonic microbes through defecation and nutrient excretion

“…This experiment was designed to mimic the natural ecosystems of the South-Eastern Mediterranean Sea where Siganus spp. have replaced natives herbivores (Rilov et al, 2018;Frid et al, 2022) . However, there are still many areas of the Mediterranean Sea (e.g.…”

“…Siganus spp. have become highly dominant on shallow ecosystems of the Levantine Sea region (representing >90% of herbivorous fish biomass over rocky habitats ;Frid et al, 2022), while the formerly only abundant native herbivorous fish (Sarpa salpa) is now very scarce (Rilov et al, 2018;Yeruham et al, 2020). Siganus have been overgrazing macroalgae to the point that ecosystems are now dominated by turf (Sala et al, 2011;Rilov et al, 2018;Peleg et al, 2019).…”

Fish depth redistributions do not allow maintenance of abundance in a region of rapid change

“…inverse; 1/Var) in our models. Thus, species with a large variance will receive a lower weight compared to species with small variance (Hedges et al 1999, Pustejovsky 2015, 2018, Frid et al 2022). We note that an increase in the relative abundance of one origin group (e.g.…”