Evaluation of Shifts in the Potential Future Distributions of Carcharhinid Sharks Under Different Climate Change Scenarios

Abstract

Climate change is currently considered one of the main phenomena affecting marine species through expansion or contraction of their distribution. Being ectothermic organisms, sharks of the family Carcharhinidae could be highly susceptible to the effects of climate change. These sharks are of great ecological importance, which is reflected in their role in the integrity of coastal and oceanic ecosystems as top predators that act to maintain the stability of the food chain, as well as providing economic value through fishing, consumption, and ecotourism. Currently, their populations are threatened by fishing pressure and anthropogenic activities, including meeting the demand for shark fins. Despite the ecological and economical importance of carcharhinid sharks, knowledge regarding how they are impacted by climate change remains scarce. Ecological niche modeling is a tool that allows analysis of future potential distributions under different climate change scenarios and could contribute to future planning activities and improved conservation outcomes for sharks. We generated models in Maxent in order to predict the potential geographic distribution of 25 carcharhinid sharks that inhabit Mexican waters, projecting this onto future climate change scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5) to calculate the potential losses and gains in their distribution areas by the year 2050. The greatest shifts in suitable areas were observed for the sharks Triaenodon obesus (gained area) and Carcharhinus porosus (lost area). Overall, under all four RCP future scenarios, six species presented gains in suitable area and 19 species presented losses. The greatest loss of suitable area for carcharhinid sharks was found with RCP8.5; however, under this high-emissions global warming scenario, seven species actually showed an increase in distribution area. Our results therefore indicate that climate change could reduce suitable areas for most of the species by 2050. Assessment of the distribution of shark species under climate change is urgently required in order to prioritize conservation efforts toward the most vulnerable species and to ensure the natural function of marine ecosystems, thus maintaining the important ecosystem services they provide to human society.

Blue carbon ecosystems and shark behaviour: an overview of key relationships, network interactions, climate impacts, and future research needs

“…Similarly, poleward shifts in tiger shark range as a result of rising SSTs were also predicted in the southern hemisphere (Niella et al, 2022). Ecological niche modelling of 25 shark species distributions under different climate change scenarios revealed losses in suitable habitat for 76% of species (Diaz-Carballido et al, 2022). While empirical data on the these effects are in general scarce, the evolutionary history of a given species may predict their responses (Gallagher et al, 2015).…”

Aligning paleobiological research with conservation priorities using elasmobranchs as a model

“…However, key questions remain about how these anthropogenic and environmental stressors affect elasmobranchs (Table 1). We have more to learn about how climate change will interact with other stressors to impact elasmobranch populations (Chin et al 2010;Rummer et al 2022), where to focus management efforts as their ranges shift (Dulvy et al 2017;Tanaka et al 2021;Diaz-Carballido et al 2022), and which species are most sensitive (Jorgensen et al 2022). Because elasmobranchs are large and mobile, it is generally not feasible to manipulate them in real time, hindering mechanistic insight into how stressors control their populations.…”

“…These models have been implemented to hindcast ecological niches (Nogués-Bravo 2009;Myers et al 2015;Monsarrat et al 2019;Skroblin et al 2021), evaluate area-based prioritization strategies (Williams et al 2013), and identify potential refugia or range shifts under future projected climate scenarios for a variety of taxa (Maguire et al 2015;Lima-Ribeiro et al 2017;Jones et al 2019; see Topic 3). There is great potential to apply these methods to elasmobranch occurrence data (e.g., Klippel et al 2016;Birkmanis et al 2020;Sabadin et al 2020;Diaz-Carballido et al 2022), especially for large migratory species, to describe their spatial distributions and protect areas that harbor threatened diversity (Fig. 3).…”

Setting Conservation Priorities for Marine Sharks in China and the Association of Southeast Asian Nations (ASEAN) Seas: What Are the Benefits of a 30% Conservation Target?

“…Sharks are heterothermic animals and temperature has a considerable impact on their distribution (Birkmanis et al, 2020;Diaz-Carballido et al, 2022). Primary productivity is also an important factor that affects shark distribution and abundance (MacKenzie et al, 2019).…”