Population dynamics of an endemic cyprinid (Hypselobarbus kurali): Insights from an exploited reservoir fishery in the Western Ghats of India

Abstract

The Western Ghats of India harbours an exceptional diversity of endemic freshwater fishes, which are threatened because of various anthropogenic stressors, including biological resource use. Lack of organized studies on the population dynamics and exploitation levels of endemic species, however, has hindered the development and implementation of systematic conservation action plans in this region. This is especially true for large cyprinid fishes threatened because of overharvest. This study examined length–weight relationships and length‐structured population dynamics of an endemic large cyprinid (Hypselobarbus kurali), based on data obtained from an artisanal gill‐net fishery in Malampuzha Reservoir. Length–weight analysis suggested the fish exhibited significantly lower exponents than expected under isometry, indicating the growth of H. kurali in the reservoir was negative allometric. The von Bertalanffy growth formula fitted to the length‐frequency data indicated H. kurali grew relatively slower than other large cyprinids in this region. Statistical analysis of recruitment revealed two peaks, implying the fish have two spawning bouts each year. Analysis of mortality and exploitation of the species revealed large‐sized individuals were targeted by the fishers, resulting in an exponential decline in the survivors in the virtual population analysis. Relative yield‐per‐recruit and relative biomass‐per‐recruit analysis indicated the current exploitation rate for the population was greater than the exploitation rate under which the stock would be reduced to half its unexploited biomass. Further, the current exploitation level was more than 60% of the expected maximum exploitation above which the population could collapse. The results of this study identify a serious need to develop and implement management plans to guide the future sustainability of the reservoir fishery of H. kurali.

Assessing the sustainability of lepidophagous catfish, Pachypterus khavalchor (Kulkarni, 1952), from a tropical river Panchaganga, Maharashtra, India

“…Uncontrolled exploitation of fishery resources by inland catch fisheries is considered as the second most noticeable threat to the freshwater fishes inhabiting the Western Ghats of India (Raghavan, Ali, Philip, & Dahanukar, 2018;Raghavan et al, 2018a;Smith et al, 2011). However, presently, the gap in the research examining the impact of biological resource use on freshwater biodiversity or livelihoods is surprising.…”

“…Fishery management is a dependent field, and in order to implement management plans and conservation actions, concrete data on demography parameters (growth and mortality rates), status of populations (stock assessments), and number of fish harvested (exploitation levels and rates) is the primary requirement (Raghavan et al, , 2013(Raghavan et al, , 2018a. Nonetheless, such data are readily available and confined to a few of the large-growing tropical cyprinids such as the members of the genus Tor (Bhat, Nautiyal, & Singh, 2000;Raghavan et al, 2011Raghavan et al, , 2018a, with complete absence of information available on other groups, including P. khavalchor which is presently categorized as the data-deficient species with possible speculation of its loss in the near future (Dahanukar, 2011;Dahanukar et al, 2012;IUCN, 2018;Menon, 1999). In this regard, the detailed investigation of the population dynamics of the data-deficient species inhabiting the Western Ghats of India is the key solution for imposing the conservation action plans.…”

“…The Western Ghats of India is well known for its exclusive biodiversity and also classified as a freshwater eco-region with more than 300 species of the freshwater fishes (Abell et al, 2008;Molur, Smith, Daniel, & Darwall, 2011;Myers, Mittermeier, Mittermeier, Da Fonseca, & Kent, 2000). Nearly 30% of the species inhabiting the Western Ghats have been categorized as threatened in the IUCN Red list (Dahanukar, 2011;Dahanukar, Raghavan, Ali, Abraham, & Shaji, 2011;, Ramprasanth, Ali, & Dahanukar, 2018a). However, several endemic and threatened species continue to be harvested at unsustainable levels through artisanal and open-access fisheries throughout the Western Ghats (Das et al, 2017;Keskar, Raghavan, Kumkar, Padhye, & Dahanukar, 2017;Kharat & Dahanukar, 2013;Prasad, Ali, Harikrishnan, & Raghavan, 2012;Raghavan, Ali, Dahanukar, & Rosser, 2011;Raghavan et al, 2018a).…”

“…Nearly 30% of the species inhabiting the Western Ghats have been categorized as threatened in the IUCN Red list (Dahanukar, 2011;Dahanukar, Raghavan, Ali, Abraham, & Shaji, 2011;, Ramprasanth, Ali, & Dahanukar, 2018a). However, several endemic and threatened species continue to be harvested at unsustainable levels through artisanal and open-access fisheries throughout the Western Ghats (Das et al, 2017;Keskar, Raghavan, Kumkar, Padhye, & Dahanukar, 2017;Kharat & Dahanukar, 2013;Prasad, Ali, Harikrishnan, & Raghavan, 2012;Raghavan, Ali, Dahanukar, & Rosser, 2011;Raghavan et al, 2018a). According to Darwall et al (2018), another most important and fundamental cause for the freshwater biodiversity crisis is the insufficient consideration of impacts on freshwater ecosystems in decision-making and policy.…”

“…The persistence of any fish species in the given habitat is dependent on the life history traits of that species (Das et al, 2017(Das et al, , 2018Kumar et al, 2014;Prasad et al, 2012;Raghavan et al, 2011Raghavan et al, , 2018a. Under the present environmental conditions, life history traits must generate sufficient recruitment for a given population to persist.…”