Invasion of non-indigenous suckermouth armoured catfish of the genus Pterygoplichthys (Loricariidae) in the East Kolkata Wetlands: Stakeholders’ perception

Abstract

Rapid spread and population increase of suckermouth armoured catfishes belonging to the genus Pterygoplichthys(Loricariidae) in the East Kolkata Wetlands (EKW) in recent times is of increasing concern, because of the notable possibility that these non-native catfishes are adversely affecting fish germplasm and commercial fishery of this unique ecosystem. To study the present status of these loricariids and the invasion and impact dynamics in EKW ecosystems, field survey was conducted over a water spread area of 670 ha, comprising 120 fishermen (N2 = 120) of 30 farms (N1 = 30), between February and October, 2017 through a pre-tested, open-ended structured schedule. A total of 943 specimens of Pterygoplichthysspp. were collected and analysed for abundance, length-weight parameters, gonado-somatic index and relative fecundity. Pterygoplichthysspp. occurred at 29 (97%) of 30 surveyed farms and approximately 70% of the farm owners perceived that these fishes posed moderate to serious economic impact. Fish production cutback, small indigenous fish (particularly,Puntius spp.) depredation and bottom structure alteration are among the major negatives perceived; a positive note in terms of soil-bound nutrient release was reported by a few fishermen (1%). Channel through which sewage water intake occurred by gravitation has been perceived to be the main route of entry (77%), with significantly higher abundance around the periphery of the pond. Almost 80% respondents perceived an increased occurrence of these fishes over the last four years, with seasonal pattern of abundance. While culling of suckermouthafter harvest was the most common method adopted to reduce population, multi-layer screening in the inlet of sewage water into pond is perceived as most sought solution for control. Average direct and indirect financial losses due to Pterygoplichthys spp. in EKW was calculated as`0.092 lakh ha-1yr-1, which points towards mounting pressure of loricariids in already dwindling economics and biodiversity of EKW.

Record and establishment of the non-native Loricariid catfish genus Pterygoplichthys (Siluriformes: Loricariidae) in the Coastal Plain of San Blas, Nayarit, Southeast Gulf of California, Mexico

“…These fish could live up to 5.25 years and grow up to 51.5 cm of SL, with a rapid growth rate of approximately 10 cm per year (Gibbs et al, 2008). The length-weight recorded a negative allometric growth of Pterygoplichthys, which was consistent with the reports of Rueda-Jasso et al (2013), Wei et al (2017) and Hussan et al (2019). This indicates that fish tend to lose weight and be fewer with greater length.…”

Suckermouth armoured catfish (Pterygoplichthys spp.) menace in freshwater aquaculture and natural aquatic systems in Andhra Pradesh, India

“…In a previous study, it was reported that 83% of fish farms in East Kolkata Wetlands were invaded by Pterygoplichthys spp. which may be primarily be due to the convivial environment (Hussan et al, 2019) [28] and primary feed abundance (Ozedilek, 2007) [29] . In the current study, Pterygoplichthys spp.…”

“…The abundance of Pterygoplichthys spp. in East Kolkata Wetlands up to 22 individuals per ha corresponding to the production of 450 kg/ha per year (Hussan et al, 2019) [28] . Pterygoplichthys spp.…”

“…populations have the ability to withstand low dissolved oxygen content (Ambruster, 1998) [33] , minimized metabolic rates (MacCormack et al, 2003) [34] , hostile feeding habit (Molur et al, 2016) [35] , rapid growth (Hussan et al, 2019) [28] , ability to breed in a variety of environments (Chaichana and Sirapat, 2012) [36] and less vulnerability to predation (Zworykin and Budaev, 2013) [32] as also withstanding poor water conditions (Welcomme and Vidthayanom, 2003) [37] . Although, Hussan et al (2019) [28] has suggested multi-layer screening of the inlet water into the ponds is most suitable solution for control but, invasion of the Pterygoplichthys spp into fish culture ponds could not be arrested even by screening of inlet waters with monofilament screen (100 mesh/inch), thus the possible way in which they register in an ecosystem seems to be intricate. Voracious grazing on benthic algae and periphyton by Pterygoplichthys spp reduces food cover available for other similar fishes and aquatic insects and thus, disrupts the food web (Hoover et al, 2014) [38] .…”

“…al. 2019) [28] , Kerala (Suresh et al 2019) [30] , Tamilnadu (Sandilyan, 2019) [61] . In the present study, invasion of Pterygoplichthys spp was assessed in terms of biomass registered in carp culture ponds as well as canal and river systems.…”