Corresponding author: Basanta Kumar Das ( basantakumard@gmail.com ) Academic editor: Predrag Simonović
© 2021 Ranjan Kumar Manna, Archisman Ray, Supriti Bayen, Tanushree Bera, Debashis Palui, Basanta Kumar Das.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Manna RK, Ray A, Bayen S, Bera T, Palui D, Das BK (2021) First record of exotic alligator gar, Atractosteus spatula (Actinopterygii: Lepisosteiformes: Lepisosteidae), from Ganga River system, India: A possible threat to indigenous riverine fish diversity. Acta Ichthyologica et Piscatoria 51(4): 385-391. https://doi.org/10.3897/aiep.51.72676
|
A new record of an exotic alligator gar, Atractosteus spatula (Lacepède, 1803), from an open wetland of the Ganga River was presented in this paper and discussed along with the environmental parameters. Entry of the exotic fish into the natural system was probably a result of uncontrolled ornamental fish trading. Considering threats of this predatory fish to become invasive and disturb riverine fish diversity, possible ways to avoid such risk have been discussed.
alligator gar, exotic fish, Ganga River, wetland
Large rivers basins harbor a significant share of the world’s aquatic biodiversity, providing important goods and services to the society, including fisheries. Ganga basin is the largest and most important river basin in India. The wetlands of the Ganga basin are mostly formed as a result of the meandering of the river or sloughs or tectonic depressions receiving huge surface runoff or freshwater from the river. The connection of the wetland to the river promotes aquatic biodiversity, especially a higher abundance of small indigenous fishes (
A single specimen of Atractosteus spatula was captured from Chharaganga Beel (wetland) (23°27′48.87′′N, 88°20′46.7592′′E), Nabadwip, West Bengal using a gillnet (mesh 10–15 cm) on 23 July 2020 during the early morning hours of fishing activity. The fish was identified in line with the methodology of
Ethical statement. During the study, no harm was made to alligator gar which has been described in this paper. After the study, the fish was released in live condition into secured captivity so that it could not reach natural open water.
The fish collected from Chharaganga wetland was identified as Atractosteus spatula, it weighed 2.25 kg, and was characterized by a long and cylindrical body (Figs
Although the information on its habitat usage is scanty, Atractosteus spatula was reported to dwell in both freshwater and marine water habitats (
Water parameters of Chharaganga Beel adjacent to the Ganga River (at Nabadwip).
Parameter | Chharaganga Beel | Ganga River (Nabadwip) | ||
Range | Mean ± SD | Range | Mean ± SD | |
Temperature [°C] | 22.7–32.6 | 27.87 ± 3.16 | 18.2–33.7 | 27.69 ± 6.32 |
pH | 6.8–9.2 | 7.97 ± 0.55 | 7.4–8.7 | 8.18 ± 0.44 |
Dissolved O2 [ppm] | 1.0–10.5 | 5.27 ± 2.15 | 5.4–9.5 | 7.01 ± 1.43 |
Turbidity (NTU) | 0.03–56.20 | 4.19 ± 8.15 | 15.48–237.00 | 94.52 ± 76.16 |
Conductivity [µS · cm–1] | 172–570 | 276.42 ± 64.56 | 177–338 | 249 ± 62.41 |
Alkalinity [ppm] | 78–188 | 129.43 ± 22.09 | 67–134 | 99.91 ± 25.83 |
Hardness [ppm] | 80–150 | 113.62 ± 19.15 | 60–140 | 91.5 ±28.81 |
Ca2+ [ppm] | 12.65–44.08 | 26.30 ± 6.79 | 14.43–36.87 | 27.33 ± 7.32 |
Mg2+ [ppm] | 4.70–28.56 | 13.42 ± 6.35 | 1.88–16.44 | 6.55 ± 4.79 |
Nitrate-N [ppm] | 0.012–0.200 | 0.072 ± 0.05 | 0.120–0.512 | 0.304 ± 0.120 |
Total N [ppm] | 0.074–2.297 | 0.616 ± 0.44 | 0.376–0.700 | 0.495 ± 0.110 |
Phosphate-P [ppm] | 0.004–0.827 | 0.087 ± 0.17 | 0.026–0.070 | 0.043 ± 0.020 |
Silicate-Si [ppm] | 1.6–24.2 | 6.028 ± 4.280 | 0.4–10.2 | 7.10 ± 3.47 |
Soil parameters of Chharaganga Beel adjacent to the Ganga River (at Nabadwip).
Parameter | Chharaganga Beel | Ganga River (Nabadwip) | ||
Range | Mean ± SD | Range | Mean ± SD | |
pH | 7.01–8.24 | 7.68 ± 0.30 | 7.60–8.70 | 8.27 ± 0.39 |
Specific conductivity [mS · cm–1] | 0.218–2.08 | 0.924 ± 0.470 | 0.058–0.274 | 0.192 ± 94.770 |
Organic C [%] | 0.10–2.00 | 0.74 ± 0.51 | 0.09–0.54 | 0.34 ± 0.15 |
Total N [%] | 0.01–0.30 | 0.10 ± 0.07 | 0.02–0.07 | 0.04 ± 0.02 |
Available N [mg · 100 g–1 soil] | 8.40–26.30 | 15.26 ± 3.53 | 2.80–7.84 | 5.79 ± 2.65 |
Available P [mg · 100 g–1 soil] | 0.13–0.54 | 0.31 ± 0.09 | 0.92–3.48 | 2.22 ± 1.35 |
The alligator gar has been presumed to have been released by some aquarium hobbyists deliberately into the wetland which is a routine method to get rid of the pet when it attained a size large exciding the capacity of an indoor aquarium. Other than willful release by the hobbyist, extreme climatic events have often been identified for entry of the exotic fishes into Indian inland open waters (
West Bengal occupies a major position in the ornamental fish trade with 55% of total production in India.
Studying fish invasions in more than 1000 river basins on a global scale,
We wish to thank the National Mission for Clean Ganga (NMCG), Ministry of Jal Shakti, Government of India for their funding support under Project No. T-17/2014 15/526/NMCG- Fish and Fisheries. Thanks to Ms. Manisha Bhor for the preparation of the fish distribution map given in the paper.