Sharkie Hotspots
Updated: Oct 20
When planning protective measures, conservationists don't always choose to protect a specific species that has been found to be threatened with extinction. Instead, they can opt to conserve areas that have been deemed to be particularly valuable. Maybe that area has high "biodiversity", so protecting the region will benefit many different species. Or maybe the area has "endemic species" that are not found anywhere else in the world, so conserving that particular habitat is vital. So when it comes to shark conservation, where in the world is their biodiversity highest? Where are sharks most abundant? And are these sharkie hotspots protected?
Making a Plan
When drawing up plans for national parks or marine protected areas (MPAs) conservationists aim to prioritise the protection of areas with especially high biodiversity or "species richness". Sometimes we may refer to this biodiversity in general terms; with a count of all the different species of plants and animals living in that habitat. On the other hand, we can also describe the biodiversity of particular groups; such as assessing the diversity of sharks in different habitats or the diversity of corals on different reefs.
It can also be important to asses if an area has a lot of threatened species living there, so conserving the region may save these creatures from extinction. It is also vital to consider whether a habitat is host to "endemic species". These are animals (or plants or fungi!) that are only found in one specific place in the world. Endemic species are especially vulnerable to extinction because their restricted geographical range limits their ability to relocate if their habitat is damaged or destroyed (Kyne et al, 2011).
For example, the Colclough’s shark (Brachaelurus colcloughi) are currently flagged as Vulnerable and their population size is decreasing. As they can only be found within 2° of latitude on the Australian east coast, in rocky reef habitats, protection of these areas may be critical for their survival (Kyne et al, 2011).
I'm Rich!
When considering all sharks and rays, highest species richness can be found in tropical regions along equatorial coastlines, but also in some higher latitudes. Biodiversity is especially high in the Gulf of Mexico, the Gulf of California, Ecuador, Uruguay, southern Brazil, South Africa, southern Mozambique, southern Namibia, Japan, Taiwan, parts of southern China, and eastern and western Australia (Derrick et al, 2020). There's your travel bucket list written!
No regions of high shark and ray species richness are found in pelagic areas - areas far offshore away from the coast (Dulvy et al, 2014; Derrick et al, 2020).
Scientists think this is because these tropical and subtropical regions are very "productive". This means that these are high energy systems that can support complex habitats and a large diversity of different species (Derrick et al, 2020).
Respect the Locals
However, when we look at endemic species richness we see a slightly different pattern. Whilst all endemic species were also found on coastlines (rater than in open ocean habitats), the species richness is actually highest outside of equatorial regions and peaks at the boundaries of tropical and temperate ecosystems. This is especially true in the southern hemisphere, where there were endemic species hotpots in Australia, South America and South Africa. These areas are also where the highest richness of endangered endemic species can be found (Derrick et al, 2020).
Scientists have identified that there are some areas that will be especially important to protect because they are critical homes for endemic species of sharks and rays. Most notably, areas with high irreplacability can be found off the north coast of South America, but also off the south east coast, in the Mediterranean, around the south of Africa, around Australia and throughout the Indo-Pacific (Dulvy et al, 2014).
Under Threat
"Elasmobranchs" (sharks, skates and rays) are one of the most threatened groups of vertebrates globally. We currently know of more than a thousand different species of elasmobranch fishes, of which around 540 are classified as sharks and 600 are classified as "batoids" (skates and rays). As many as 1/4 of all these species are considered threatened - flagged either as Vulnerable, Endangered or Critically Endangered on the International Union for the Conservation of Nature’s Red List of Threatened Species (Dulvy et al, 2014).
This is because they are unsustainably overexploited in fisheries and their habitats are seriously degraded by human activity (thanks to climate change, littering, and chemical and noise pollution). Elasmobranchs are also especially vulnerable because they are very slow growing, late to become sexually mature, have long life-spans and have relatively few offspring throughout their lives. This means they struggle to recover if the population experiences severe declines (Dulvy et al, 2014).
Safe Havens
Currently, MPAs only encompass around 3% of the oceans surface. However, the great news for elasmobranchs is that the MPAs that already exist in the Gulf of California, South Africa, Australia and the Galapagos in Ecuador already encompass some of the most biodiverse regions. However, when we consider other areas with high species richness, especially for endangered and endemic species, it becomes clear that there are many important areas that are not yet adequately protected (Kyne et al, 2011; Dulvy et al, 2014; Derrick et al, 2020).
Whilst we would love to be able to protect every single habitat on the planet and save every endangered species, the reality (sadly) is that conservationists are forced to juggle their own desire to protect nature with logistical challenges and finite funding opportunities, whilst coming up against varying opinions and needs of multiple different stakeholders: fishers, politicians, big business, the local community... This means that we simply cannot do it all and we need to triage in order to make the biggest positive impact with the resources available to us.
Currently MPAs do not seem to cover a sufficient area or to be located in the correct places in order to ensure we are protecting sharks and rays as efficiently as we can. But the good news is that there is an army of amazing and passionate people fighting every day to change this. Scores of scientists, NGOs and charities are working tirelessly on the 30x30 Ocean Campaign, with the goal to create a global network of MPAs that covers 30% of our ocean by the year 2030. So hopefully, very soon, we will start to see some of the most important shark and ray habitats enveloped under an umbrella of protection within these marine parks. wThen maybe. If shark populations started to recover around the world, maybe we could even find some new shark hotspots beginning to appear.
You can learn more about Marine Protected Areas at the Atlas of Marine Protection. You can also support the process of implementing new MPAs by supporting your local conservation groups in the UK, Europe, USA, South Africa.
References
Derrick DH, Cheok J & Dulvy NK (2020). Spatially congruent sites of importance for global shark and ray biodiversity. PLoS One, 15:7, e0235559. Access online.
Dulvy NK, Fowler SL, Musick JA, Cavanagh RD, Kyne PM, Harrison LR, Carlson JK, Davidson LN, Fordham SV, Francis MP & Pollock CM (2014). Extinction risk and conservation of the world’s sharks and rays. elife, 3, p.e00590. Access online.
Kyne PM, Compagno LJV, Stead J, Jackson MV & Bennett MB. (2011). Distribution, habitat and biology of a rare and threatened eastern Australian endemic shark: Colclough’s shark, Brachaelurus colcloughi Ogilby,1908. Marine and Freshwater Research, 62, 540–547. Access online.
By Sophie A. Maycock for SharkSpeak.