Identification of critical habitat in a data-poor area for an Endangered aquatic apex predator.

Conservation often focuses on “critical habitat” including areas important for the reproduction of threatened taxa. As for many aquatic species a priority of shark conservation is the protection of nurseries, yet few countries can support the costly fieldwork required to identify these according to strict criteria. Alternative approaches are therefore required where resource, capacity and security constraints exist. This study collates low-resolution data from alternative, remotely collected and inexpensive existing sources (fish market surveys, literature, museums, anecdotal accounts), to evaluate a possible nursery for the regionally Endangered bull shark (Carcharhinus leucas) in the Tigris-Euphrates system and adjacent northwestern Persian/Arabian Gulf (Iraq, Iran, Kuwait), a data-poor area long characterised by conflict and inaccessibility. Evidence is presented that aligns with two of the three nursery definition criteria (abundance and repeated use), along with other data supporting known C. leucas reproductive behaviour. While the necessarily low resolution data cannot answer the full suite of strict nursery criteria nor identify precise nursery locations, they nevertheless collectively provide compelling evidence for a broad area of importance to young and juvenile C. leucas. This area is both highly threatened (e.g. by damming, climate change, fisheries) and of potential major significance, given the apparent absence of similar estuary habitat for thousands of kilometres of arid northwestern Indian Ocean coast. The inexpensive desk-based approach to identifying critical habitat provides another toolkit option for conservationists and could best be applied to distinctive threatened aquatic taxa, especially in the developing world where conservation is often resource-limited.