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Growth parameters, mortality, growth performance index and exploitation ratio of Oreochromis niloticus were assessed based on the length-frequency data collected fortnightly from the Allahabad stretch of the Yamuna, India, during September 2011 to August 2013. The size of the catch ranged between 70 and 495 mm total length. The data was analyzed using the Electronic Length Frequency Analysis module in FiSAT software. Asymptotic length and growth coefficient were estimated as 562 mm total length and 0.58 year−1, respectively. Total mortality, natural mortality and fishing mortality coefficients were 3.74, 1.015 and 2.725 yr−1, respectively. The growth coefficient index was calculated as 3.26. The exploitation ratio worked out as 0.667, indicated that the stock was slightly overexploited. Estimated growth at the end of I, II and III years was 247, 386 and 463 mm total length, respectively. The observed multi-year survivorship based on the length frequency data from the river Yamuna in O. niloticus suggested that it has successfully established in the non-native environment and is rapidly spreading in other tributaries of the river Ganga. The recruitment pattern was observed to be continuous throughout the year, with several micro-cohorts and two overlapping peaks of unequal pulse strengths. Estimated maximum sustainable yield for this species in the Allahabad stretch of the river Yamuna was 27.13 t. This study can form an important base for future research work in the management of this invasive species in the Gangetic river system in India.

Background. The investigation on different aspects of the reproductive biology is valuable information in the development of breeding technologies towards initiating conservation and other management measures of the indigenous fish stocks. The zig-zag eel, Mastacembelus armatus (Lacepède, 1800), is a commercially important fish species in the river Ganga of India. But, the data on the reproductive biology of this species is limited. Hence, this study was done to gather information on some aspects of the reproductive biology of M. armatus to address the gap in the current knowledge. Materials and methods. Some biological traits relating to the reproduction of M. armatus from the river Ganga were studied based on the monthly sampling for one year from April 2015 to March 2016. A total of 286 fish specimens were collected, comprising 167 males and 119 females. Weight–length relations for both sexes were estimated with the aid of regression analysis. The fecundity was calculated following the gravimetric method. The length at 50% maturity (L50) for the male and female were assessed employing maturity status data. The spawning season was predicted by employing gonadosomatic index and maturity status data. Results. Monthly sex ratio (F ÷ M) ranging between 0.22 ÷ 1 and 2.75 ÷ 1 with a mean of 0.71 ÷ 1 observed in the population was significantly different from 1 ÷ 1. Analysis of mean monthly gonadosomatic index (GSI) and the existence of matured (IV and V) and spent (VI) individuals, indicated year-round spawning with two breeding seasons. The first breeding season, in the river Ganga, occurred between February and May, and the other between July and November. The L50 of Mastacembelus armatus female and male were determined as 362.2 and 385.6 mm total length (TL), respectively. The reproductive potential in terms of absolute fecundity ranged between 2546 and 6058 with a mean of 3962 ova. Conclusion. The current investigation helps to report the size at maturity in the female and the male for the first time from Indian waters. Mastacembelus armatus represents a low fecundity, indicating that this species has a comparatively lower reproductive potential, making it more vulnerable to excessive fishing pressure. For the sustainable management of this species, it is necessary to utilize the resources wisely and avoid overfishing in the river Ganga.

The length-weight relationships (LWRs) of Otolithoides pama (Hamilton, 1822) from the Hooghly-Matlah estuarine system of West Bengal were estimated. The study is based on 618 samples (298 male and 320 female) collected at monthly intervals for a period of 18 months (November 2016 to April 2018) from artisanal catch. No significant difference (p>0.01) was observed in growth rate for both the sexes. The ‘b’ values were estimated at 2.88, 2.84 and 2.86 with ‘r2‘values as 0.96, 0.95 and 0.95 for male, female and pooled samples respectively. The growth pattern was found to be negatively allometric. The month-wise mean ‘K’ value ranged from 0.70±0.07 to 0.78±0.07 for male and 0.71±0.05 to 0.89±0.11 for female. The length-wise estimated mean ‘Kn’ value varied from 0.92 to 1.17 for male and 0.76 to 1.29 for female indicating the moderately good condition of the fish in the study area. The results can be used for sustainable management and conservation of this commercially important species in this estuary

Pen culture for in situ raising of stocking material was conducted in Sareni Jheel, located in the Rae Bareli District of Uttar Pradesh. Sareni Jheel, being rich in organic carbon (4.5%) and nutrients, higher values of silt (29%) and clay (15%) were recorded. Rich oxygen levels, alkaline pH, high organic matter, moderate to high chemical parameters suggested moderately productive nature of this wetland. Pen with high-density polyethylene (HDPE) net was installed in an area of 0.1378 ha and stocked with advanced fry of the Indian major carps, rohu Labeo rohita and catla Catla catla in the ratio of 1:1 @ 25 nos. m-2. No significant changes in water quality parameters were noticed within and outside the installed pen. Mean weight at stocking of rohu and catla was 2.88±1.41 g and 2.1±1.16 g, which increased to 57.2±13.84 g and 67.38±25.79 g respectively, in 120 days. The average feed conversion ratio (FCR) recorded was 1.08 with overall survivability of 69.52% in rohu and 74.74% in catla. Benefit-cost ratio and return on investment were calculated as 1.69 and 0.69, respectively. Intervention through pen culture resulted in the increase in fish productivity of Sareni Jheel from 310 to 833 kg ha-1.

Nile tilapia Oreochromis niloticus is the dominant invasive species of the river Yamuna. Gut analysis showed that the majority of the food items ingested consisted of Chlorophyceae, Myxophyceae, Bacillariophyceae and detritus. Among the diatoms—Synedra spp. (80.75 %), Melosira spp. (73.5 %), Cyclotella spp. (73 %), Meridion spp. (71.75 %) and Nitzchia spp. (73.25 %), the green algae—Ankistrodesmus spp. (71.00 %), Coelastrum spp. (61.5 %), Scenedesmus spp.(52 %), Tribonema spp. (49.5 %), Protococcus spp. (58.5 %), Oocystis spp. (49.75 %) and Pediastrum spp. (49.5 %) and among blue green algae, Oscillatoria spp. (70.5 %), Anacystis spp. (61.5 %) and Phormidium spp. (46.5 %) showed high frequency of occurrence. The Gastrosomatic Index in males and females ranged from 0.23 to 0.93 and 0.25 to 1.1 respectively with no significant difference between males and females throughout the year (t test, p > 0.05). In addition to this, higher percentage of males and females showing low feeding intensity during all the months except in January indicted the species to be the poor feeder. However, the condition factor >1 suggested the species to be in good condition throughout the year in both males and females. Dominancy of detritus and pollution indicator genera Synedra spp., Anacystis spp., Ankistrodesmus spp., Melosira spp., Nitzchia spp., Oscillatoria spp., Phormidium spp. and Scenedesmus spp. suggested Nile tilapia to be the cleaner of the polluted river Yamuna.

The brinjal fruit and shoot borer, Leucinodes orbonalis is the major pest of eggplant in South Asia. Analysis of female pheromone gland extracts prepared from insects of Indian and Taiwanese origin confirmed (E)-11-hexadecenyl acetate (E11-16:Ac) as the major pheromone component with 0.8 to 2.8% of the related (E)-11-hexadecen-1-ol (E11-16:OH), as previously reported from Sri Lanka. The average quantity of E11-16:Ac extracted per female was estimated to be 33 ng, with a range of 18.9 to 46.4 ng when collected 2 to 3 hr into the scotophase. In field trials conducted in India, blends containing between 1 and 10% E11-16:OH caught more male L. orbonalis than E11-16:Ac alone. At the 1,000 microg dose, on white rubber septa, addition of 1% E11-16:OH to E11-16:Ac was found to be more attractive to male L. orbonalis than either 0.1 or 10% E11-16:OH. Trap catch was found to be positively correlated with pheromone release rate, with the highest dose tested, 3,000 microg, on white rubber septa catching more male moths than lower doses. Field and wind tunnel release rate studies confirmed that E11-16:OH released from white rubber septa and polyethylene vials at approximately twice the rate of E11-16:Ac and that the release rate of both compounds was doubled in polyethylene vials compared to white rubber septa. This difference in release rate was reflected in field trials conducted in Bangladesh where polyethylene vial dispensers caught more male moths than either black or white rubber septa, each loaded with the same 100:1 blend of E11-16:Ac and E11-16:OH in a 3,000 microg loading.