Introduction

Acropoma japonicum commonly called Glowbelly / Lanternbellies belongs to the family Acropomatidae is popularly known to occur in deeper waters. It inhabits sand and sandy mud bottoms. A peculiar character of this fish that made it different from other species was the position of anus, anus was very close to the pelvic fin origin, a light organ was present between pelvic fins. Two luminous organs placed longitudinally from thorax to beyond the anus. A. japonicum is distinguished from other species of Acropomatidae family in having light organ and ctenoid scales (Narges et al., 2012). Laternbellies are known for their ventral luminous organs. The family comprises 31 species from seven genera throughout the world. Out of seven, the genus Acropoma contains five valid species, all occurring in the Indo-Pacific area; of which only Acropoma japonicum was reported previously from Indian waters (Prasanna et al., 2012). Acropomatidae are widely distributed and deep water fishes inhabiting a depth of 20-700m, mesopelagic depth, fishing by midwater trawlers off Iran (Narges et al., 2012). According to Noboru et.al.,(2005) the catch of A. japonicum in number and mass, with a minority of such demersal fishes as lizardfishes, cardinal fishes, pony fishes, gobies, lefteye flounders and soles.

A perusal of literature (Weber & de Beaufort, 1929, 1941; de Beaufort & Chapman, 1951, Gunther 1859 Smith & Heemstra, 1986, FAO Species identification Sheet Vol.I, 1983) indicates the occurrence of the species in the Indo-West pacific from East Africa to Japan and South to Northern Australia. In India, though known from the west coast its bathy demersal fish is recorded for the first time from east coast as per no previous records are available.

The maximum size of the fish as reported (Gunther, 1859) is 20cm that usually occurs in the depth range of 100-500m and minimum population doubling time reported to be 1.4 – 4.4 years (Assuming T_max x >3 years).

In the present study, an attempt has been made to define identification characteristics and characterizing its population by studying its morphometric, meristic and size distribution etc.

Material and Methods

The specimens of A. japonicum representing different size ranges was obtained from the survey vessels deployed for bottom trawling; particularly during the cruises of MFV. Matsya Jeevan, MFV. Samudrika, and MFV. Matsya Shikari which are the trawlers of 36.5m (OAL), 28.8m (OAL) and 39.5m(OAL) respectively from the years 1998 - 2012.

The species was record at a depth of 130-131m about 14 nautical miles (kn) off Vatturupallepalem, Andhra Pradesh between the Lat. 14°56’N / Long. 80°20.7’E and Lat. 14°52’N/ Long. 80°19’E in a single haul with trawling duration of 1.5 hours resulted in a catch of 65kg. A random sampling collected from the total of 450 specimens. Measurement of total length (TL) varied from 5 to 14cm. The species recorded off Kalingapatnam by Matsya Shikari was utilized for biological studies. In the west coast of India, the survey vessel Matsya Nireekshani a combination trawler of 40.5m (OAL) recorded a total of 583 specimens, ranging from 5 to 12.5cm with the total length sampled at random from the depth between 74 and 85m, in the area between Lat. 20°.00’N / Long. 70°56’N and Lat. 22°14’N / Long.68°08’E.

The length frequency data sampled from east and west coast that approximately follows the so called Gussian Distribution. The mathematical expression for the Gussian Distribution used in the present study

  …… (1).

Different morphometric and meristic characters of the 52 sampled specimens were studied following the standard least square method described by Snedecor (1967), Laevastu (1965) and followed by many worker viz., Dwivedi and Menezes (1974), Chondar (1974), Sivaraj and Dwivedi (1982), Acharya and Dwivedi (1984), Gulati and Acharya (2001) etc.

The regression of the morphometric characters (Y) viz., fork length, standard length, body depth, head length, length of the caudal peduncle, taking the total length as the independent character (X) whereas, for the morphometric characters viz., pre-orbital length, inter-orbital length and eye diameter, taking the Head length as the independent character (X) were worked out, using the formula:

   …… (2).

Where ‘Y’ is any dependent meristic character, ‘a’ and ‘b’ are constants.

The length-weight relationship was established by fitting equation of the form

 ……. (3).

The length-weight relationship was established by fitting equation of Le Cren (1951).

Where ‘W’ is the weight of the fish (g) and ‘L’ its length (cm), ‘a’ and ‘b’ are the constants. The equation (3) was expressed in the linear form by using logarithmic transformation as given below:

 …….. (4).

The estimates of the constants ‘a’ and ‘b’ were obtained by the method of the least square.

The data collected are also considered for biological investigations viz., sex ratio, maturation, spawning, food and feeding habits of the species using standard methodologies. The stomach contents of 52 specimens of glow fish caught during Dec’2000 from east coast were cut open and analyzed to understand the major food items of the species.

Results and Discussion

A better description of length frequency / survey data, the number caught per trawl haul is often obtained, assuming the so-called “Gussian Distribution”. Table -1&1(a); Fig -1&1(a) show the theoretical frequencies with observed frequencies, as can be seen, theoretical frequencies give a fair fit to the observed length-frequencies. This picture is often noticed, when recording length-frequencies of the fish, originating from one cohort i.e., fish of the same age, as seen in the present study. The mean length of the species observed to be 8cm and 9.5cm of set observations from east and west coast of India respectively.

The relationship between total length and other body measurements was found to be highly correlated, Table -2 & Fig.2, the coefficient of determination (r²) varied from 0.6999 to 0.991. The coefficient of determination (r²) is an indicator of the goodness of fit it of regression equation to the observed data. The closer it is to 1, the better is the fit. In most of the regression viz., Standard length, Fork length, Body depth, coefficient of determination was very close to 1, indicating that these characters, under study can be efficiently estimated based on the total length as independent variable (X) and regression of different relevant morphometric characters viz., pre-orbital length, eye diameter and inter-orbital length on head length was not found highly correlated. The coefficient of determination varied from 0.6999 to 0.858 (Table-2) the character pre-orbital lengths, coefficient of determination being close to 1, on the head length as independent variable (X) may yield estimate based on head length as independent character (X).

The morphometric relationships (Table-2) revealed that in respect of total length, the fork length grows faster (b=0.87) than standard length (b=0.81), whereas, body depth grows faster (b=0.27) than head length (b=0.22) and length of I^st dorsal fin grows faster (b=0.13) than II^nd dorsal fin (b=0.11), in respect of head length as independent character (X), revealed that the pre-dorsal length grows faster (b=0.48) than the inter-orbital length (b=0.27) and the eye diameter (b=0.31).

The meristic characteristics of the A. japonicum recorded as dorsal spines 9 with no variation, dorsal soft rays 10, with no variation; anal spines 3 followed by 7 soft rays without any variation.

The length-weight relationship for males, females and pooled was found to be, and respectively. The coefficient of determination for male, female and combined found to be ,  and  respectively. The coefficient of determination for male, female and combined found to be 0.7163, 0.7227 and 0.7747 respectively, indicating that only 72%, 72% and 77% of variation in weight is explained by the total length in respect of male, female and combined.

The species found to be mainly feeding upon the items like juveniles of the shrimp acetus and occasionally on detritus.

As evident from the literature, there is practically no information available on maturation and spawning of the species from Indian waters and in the present study also enough specimens of the species could not be studied to understand the spawning of the species. Noboru et al., (2005) in Japan waters observed that precocity and short life span is notable because it is a higher consumer that is generally expected to show later maturation and longer life.

The females were found dominate the males in all the size groups, with an aggregate sex ratio 1.3:1.

Acknowledgement

The Authors are grateful to the Director General, Fishery Survey of India for encouragement. The authors also wish to express sincere thanks to Shri D.K. Gulati, Zonal Director FSI, and Kochi for the help in statistical analysis. The help rendered by Shri N. Jagannadh, Junior Fisheries Scientist is also acknowledged. The skippers and crew of the survey vessels MFV., Matsya Jeevan, MFV. Samudrika and Matsya Nireekshani are highly appreciated for their co-operation during data collection.

Reference

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