The aquaculture industry plays a vital role in meeting the nutritional demands of the growing global population. Lepidocephalichthys thermalis (Valenciennes, 1846) popularly known as Ayirai Meen in Tamil Nadu and commonly referred to as Indian Spiny Loach in India, presents a promising opportunity for sustainable aquaculture. Belonging to the Cobitidae family, this species thrives in shallow water and is highly valued as both an ornamental and edible freshwater fish in Tamil Nadu. These fishes are sold live in markets at Rs.1500 -2000/kg, highlighting their economic significance. Beyond its market value, L. thermalis serves as a vital subsistence fishery for rural communities, providing employment and ensuring food security. This species is distributed across Tamil Nadu, Andhra Pradesh, Maharashtra, Odisha, West Bengal, Kerala, Karnataka, Telangana and Bihar. Currently, domestic consumer demand is met exclusively through wild-caught, raising concern about the potential depletion of the natural population. Furthermore, the scarcity of water and lands poses significant challenges for the expansion of aquaculture, as much of the available freshwater resource is allocated to agriculture, leaving limited resources for aquaculture. Ever-increasing human population, the aquaculture sector must scale up production to ensure nutritional food security for millions of people in the future. Enhancing production, expanding consumer choice and conservation of native fish species can be achieved through species diversification, culture practices, and seed production. Sustainable intensification of aquaculture has become a priority, and identifying potential candidates for farming and marketing is crucial. L. thermalis fits this criterion but faces challenges in propagation due to the lack of seed availability and standardized farming practices.
Our study aimed to standardize farming practices and seed
production of L. thermalis, paving the way for its sustainable cultivation and
conservation. Field-based research revealed that ideal pond conditions for this
species include a 15 - 40-m2 earthen pond area with a water depth of 0.6 -0.7
m. The optimal stocking density is 70-72 g/m2, or 2 kg for 22 m3,
yielding 225-230 g/ m2 or 10-11 kg / 22 m3 at the end of
a three-month culture period. This species is also suitable for polyculture
with Catla catla and Labeo rohita.
Growth studies in a modified iron-frame cage system yielded a
net production of 384 g in 0.4m3 of water. The preferred feed combination is
GNOC: CSOK (60:40) ratio, provided at 10-12 % of body weight twice a day.
Success in natural induced breeding depends on the careful selection of male
and female fishes. Histological studies confirmed that L. thermalis is an asynchronous spawner, and attains first maturity
at a size of 4.5 cm. The ideal brood stock density is 150 -200 Nos/m2,
and temperature manipulation from 26ºC to 22ºC accelerates maturation. The
species grows a maximum size of 7.2 cm and 3 g. Males and females reach sexual
maturity at 4.5 cm, weighing 1.24 g and 1.38 g, respectively, with a minimum
maturity size of 3.3-3.5 cm. Fecundity ranges from 2000-5000 eggs, and natural
spawning occurs twice a year (June to August and October to December).
Artificial-induced breeding was performed by using of
synthetic hormone WOVAFH (Biostadt ®, India) at the rate of 0.02 ml. Loach
larvae thrive on a diet of copepods and cladocerans. Embryonic developmental
stages were observed, with egg hatching 48 hours post-fertilization and larvae
becoming visible on the 10th day after spawning. The water requirement for
producing 1000 L. thermalis was
significantly low ranging from 498 L to 1,397 L. Optimal water velocities for
breeding and growth were determined to be 20 cm/s, resulting in the highest
gonadosomatic index (GSI) of 11.24 ± 0.42, absolute fecundity of 1286.33 ±
96.64, relative fecundity of 1928.46 ± 35.87, and ova diameter of 653.43 μm.
Water quality parameters essential for successful breeding
included pH levels of 7.5 and 8, alkalinity of 165 ppm to 210 ppm, hardness of 165
ppm and 195 ppm and a stable temperature of 26ºC. Transportation of loach seed
(2-3 cm) was optimized, with 1200 - 1500 pieces in a bag containing 6-6.3 l of
water and 14 l of oxygen, ensuring survival for 12 hours. The ideal anaesthetic
dosage for loach fish was found to be 0.2 ml at 24ºC, with size and dose
interaction significantly affecting sedation and recovery times.
For the first time, proximate analysis of cultured L. thermalis revealed as crude protein
(20.56 ± 0.219), fat (2.67± 0.049), moisture (74.49 ± 0.353) and ash (1.29 ±
0.035). Farmed fish had a higher MUFA content (40.8 g/100g lipid) compared to
wild fish (32.86 g/100g lipid). The n3/n6 ratio was also higher in farmed fish
(1.8) than in wild fish (1.19). Economic analysis of a 40m2 culture yielded a
net profit of Rs. 8000, demonstrating the economic viability of farming L.
thermalis. This study provides valuable insights for entrepreneurs and fish
breeders, emphasizing the potential for sustainable farming and seed production
of L. thermalis. These efforts not only conserve the native fish population but
also reduce pressure on wild stock, contributing to the sustainability of
aquaculture in India.
Author (s)
Details
Mr. P.
Velmurugan
Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Kanyakumari Parakkai
Centre for Sustainable Aquaculture, Kanyakumari, Tamil Nadu, India.
Dr. Somu
Sunder Lingam, R.
Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Barur Centre for
Sustainable Aquaculture, Krishnagiri, Tamil Nadu, India.
Dr. Cheryl
Antony
Tamil Nadu Dr. J. Jayalalithaa Fisheries University, Directorate of
Sustainable Aquaculture, Nagapattinam, Tamil Nadu, India
Please see the book here:- https://doi.org/10.9734/bpi/mono/978-93-49238-97-8
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