Subspecies is a taxonomic rank below species that is generally used for populations that are geographically isolated and possess distinct morphological characteristics. The designation of subspecies can be important for conservation efforts as it allows researchers and policymakers to recognize the specific needs of distinct populations. For example, the Endangered Species Act establishes protections for more than 170 subspecies that are listed as threatened or endangered, while the IUCN Red List includes assessments for more than 3,300 subspecies.

 

One example of a subspecies that has been assessed in the IUCN Red List is the Black Sea bottlenose dolphin, a subspecies of the common bottlenose dolphin. The Black Sea bottlenose dolphin occupies the Black Sea proper, the Kerch Strait along with the adjoining part of the Azov Sea, and the Turkish Straits System (see map below; the distribution of the Black Sea bottlenose dolphin is highlighted in red). They were first denominated as a distinct subspecies in 1940 based on physical characteristics such as their relatively small body size; since then, morphological and genetic analyses have provided further evidence of the differentiation of the Black Sea bottlenose dolphin from other populations.

 

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While the common bottlenose dolphin is listed as least concern under the IUCN criteria, the Black Sea bottlenose dolphin is currently endangered. Historically, Black Sea bottlenose dolphins were extensively hunted by all Black Sea countries for manufacturing a variety of products, such as oils, paint, glue, medicine, soap, and more. In 1983, cetacean fisheries were banned in this region and commercial hunting of Black Sea bottlenose dolphins became illegal, however, many individuals would still be live-captured for military, commercial, and scientific purposes. Currently, the main threats to this population are incidental mortality in fishing gear, particularly in bottom-set gillnets, and habitat degradation as a result of pollution, coastal development, vessel traffic, depleting prey fish stocks, and invasions by non-native species. Additionally, Black Sea cetacean populations, including the Black Sea bottlenose dolphins, have been severely impacted by the 2022 Russian invasion of Ukraine, both directly from injuries caused by explosives and indirectly from acoustic trauma as a result of increased sonar activity. While their total population size is unknown, estimates suggest that there are at least several thousand individuals and that there has been a 50% reduction in population size since the 1940s.

 

In response to historical and current population declines, Black Sea countries like the former USSR, Bulgaria, Romania, and Turkey have banned commercial hunting of cetaceans since the 1960s and 1980s, vowing to international agreements like the Convention on Biological Diversity and the Berne Convention. Notably, they've worked to curb deliberate catching and trade of Black Sea bottlenose dolphins, enforcing a zero export quota in 2002. Furthermore, in 2002, the International Whaling Commission acknowledged the need to manage the Black Sea Bottlenose Dolphin population as a distinct entity. While national measures and Red Data Books offer protection, legal enforcement remains a challenge. Currently, ongoing efforts aim to establish conservation projects for Bottlenose Dolphins and Harbour Porpoises in specific regions.

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Subspecies designation plays a crucial role in implementing more effective conservation strategies for threatened and endangered species. For example, in the late 20th century, the California Condor was on the brink of extinction with a population size so small that it was designated as a separate subspecies; as a result of targeted conservation strategies, such as captive breeding programs, habitat protection, and rigorous monitoring and research efforts, the population size has seen a significant increase. By recognizing and delineating subspecies, conservation efforts can be tailored to address the unique ecological, genetic, and geographic characteristics of distinct populations within a species.