Tropical hilsa shad (Tenualosa ilisha): Biology, fishery and management

Abstract

Tropical hilsa shad, which is an anadromous fish migrating from the sea to spawn in freshwater river, constitutes an important fishery in some Asian and Middle East countries, particularly in Bangladesh. But, historical information on hilsa biology and ecology has confronted the scientists and policymakers with research and management challenges. We have reviewed both the old and recent findings on hilsa fishery to document the status of knowledge and potential gaps, necessary to comprehend for formulating a more effective fishery management plan. Thus, there has been a decline in hilsa catches in the riverine system associated with shift in fish migration routes, indiscriminate harvesting of brood and juvenile fish, and degradation of habitat. Specifically, the riverine hilsa catches peaked in the 1960s, declining thereafter, and became relatively abundant in marine waters since 1990s. Biological data indicated that hilsa goes through multiple reproductive cycles; therefore, a comprehensive understanding of reproductive biology, recruitment by various cohorts, stock abundance and habitats across the life cycle are necessary to accurately impose fishery regulatory measures, such as fishing ban in spawning season in Bangladesh. Moreover, domestication initiative is important for artificial seed production and mariculture development of hilsa that can not only offer economic return to small‐scale farmers but also reduce the growing pressure on capture fishery. Importantly, the arrangement of co‐management is found ideal as fishermen, scientists and managers can work jointly to improve the regulatory processes and to sustain the hilsa fishery over time.

Primary productivity connects hilsa fishery in the Bay of Bengal

“…However, operational limitations of gears made difficulties to determine the abundance, extent of seaward migration and fishing potential of hilsa in offshore and high seas due to lack of data and observations. Consequently, Hossain et al 33 recommend for comprehensive study in determining the range of hilsa migration with spatial and www.nature.com/scientificreports www.nature.com/scientificreports/ temporal distribution across the life cycle. It is evident from the present study that being plankton feeder, hilsa tend to follow plankton rich areas and keep moving from one place to another in search of productive zones and continue to grow.…”

Understanding Social-Ecological Challenges of a Small-Scale Hilsa (Tenualosa ilisha) Fishery in Bangladesh

“…As the single most important fishery, the hilsa catch alone constitutes approximately 12% (0.5 million tons) of the total fish production of 4.134 million metric tons as of 2016–2017 [9]. Fisheries have a total annual value of USD 2 billion, thus accounting for more than 1% of Bangladesh’s GDP and employing approximately 0.5 million fishers and 2.5 million people in the value chain [10]. As an anadromous species, hilsa inhabits a range of habitats and migrates from marine to freshwater for spawning.…”

“…The primary fishing gear includes drift gillnet and set gill nets with different modifications with local names. Many people find employment in hilsa fish marketing chain as fishers, assemblers, processors, traders, intermediaries, transporters and day laborers, including women and children [10,11]. Recently hilsa has been globally recognized as the geographical indicator (GI) product for Bangladesh [12].…”

Distribution and length-weight relationships of Hilsa shad Tenualosa ilisha in the Bilah River, Labuhanbatu Regency, North Sumatera Province, Indonesia

“…In Asia, there were five species of Hilsa shad have been described, namely; Tenualosa ilisha, T. macrura, T. toli, T. reevesii and T. thibaudeaui. In Indonesia, Hilsa shad are only found on the east coast of Sumatera, including T. macrura in the Estuarine waters of Bengkalis, Riau Province; T. ilisha in Labuhanbatu, North Sumatera and T. toli in the Pemangkat area, Kalimantan (Suwarso, 2014;Hossain et al, 2019). Tenualosa ilisha is one of the fish that has become the icon of Labuhanbatu.…”