Saturday,15 December 2018, 8 : 22 PM

Etroplus suratensis

A sapayensis
Etroplus suratensis
Image Credit: wikipedia

Introduction



Etroplus suratensis is the largest fish in its genus, it has a average TL(Total length) of 8.0 ".
It can reach a maximum size of 16".
Etroplus suratensis is found in Southern and western parts of India and Sri Lanka.
It is a very important food fish and has been declared as " Official Fish" of Kerala State, India.


Taxonomy

(Click for details of Cichlid taxonomy)

Etroplus suratensis was first described by Bloch in 1790 as Chaetodon suratensis.
The genus name is derived from the words 'etron' meaning belly and 'oplon' for arms. This refers to the spines that are present on the anal fin, i.e the long spinous anal-fin.
The species name is derived from city of surat which is the type locality for this fish.



Description

Shape :-

Body is very deep, short, oval and strongly compressed.
Depth of body is 55 % of SL (Standard length).

Eyes are large and placed laterally, eye diameter is 28.06 % of HL (Head length) .

Mouth is small and terminal .

Teeth are small and fine (villiform) and found in a single row at front but there are two or three rows at the back side in both jaw. There are no teeth on palate (roof of mouth).

Dorsal fin is inserted above pectoral fin base, with 18-19 spines and 14-15 soft rays. The spinous base is longer than soft rayed base. Soft Dorsal fin is pointed and reached just beyond the caudal fin base.

Anal fin has 12-13 spines and 11-12 soft rays. Soft Anal fin is pointed and reaches just beyond the caudal fin base.

Pelvic fins are located on thorax and have 16 rays.

Caudal fin is slightly concavely curved but not forked (emarginate).

Scales are weakly ctenoid and are of moderate size, they extend to the base of soft dorsal and anal fins. There are 35-40 scales in longitudinal series.

Lateral line is interrupted as in all cichlids. It has 6-18 scales after which it continues as small round hole in each scale. The upper lateral line is separated by 5 scales rows from dorsal fin base, and lower lateral line is separated by 17 scales from pelvic fin base.

A remarkable features of this family, is the development of the front part of the gas bladder and corresponding changes to the posterior of the neurocranium(back part of the skull that houses the brain) to create a direct connection between the gas bladder and inner ear .
This feature is not seen in any other Cichlid families. This allows fish of this genus to have remarkable hearing power.



Distribution & Habitat

Etroplus suratensis Etroplus maculatus is endemic to India and Sri Lanka.
In India it is found across western coastal parts, stretching down to South, Gujarat, Maharashtra, Goa, Karnataka, Andhra Pradesh, Taminadu and Kerala.
In Srl Lanka it is mostly restricted to Western coast extending to North.

Habitat : Etroplus suratensis inhabits coastal lagoons, lower reaches of river and brackish estuaries.
It is known as "euryhaline" i.e it lives in both brackish water as well as freshwater.
It is often with seen other cichlids of its genus.

Diet

Etroplus suratensis is omnivorous however it shows a preference for algae and plant matter.
It has a relatively long coiled gut, having a mean RLG (Relative Gut Length) of 4.3.
The structure of alimentary canal has a connection with feeding habit of fish.
A long and coiled gut is suited for better digestion of vegetable matter.

Dasgupta(2004) observed that the RLG value increased with the increase in vegetable matter and decreased with animal matter.
Generally the RLG for omnivorous fish varies between .7 to 4 times the length of animal.
E. maculatus has a RLG 1.25 which demonstrates its omnivorous nature.
Stomach content analysis contained detritus, algae, small invertebrates, animal and plant organic matter. it is often seen biting at roots of submerged plants. The mouth and dental structure of E suratensis also reflects its feeding pattern.
The frontal sharp teeth are adapted for feeding on higher plants.
The pharyngeal teeth are equipped for grinding and crushing mollusc shells.

Hence a varied diet with algae and plant matter is recommended.



Conservation Status & Threats



Etroplus suratensis is listed as “Least Concern ” in “The IUCN Red list of Threatened Species” 2013.2
Etroplus suratensis has been assessed as “Least Concern ” because of its widespread distribution across a wide variety of habitats in almost the entire southern part Indian peninsula and Sri Lanka.
However a declining trend has been observed in the Kerala.
Population of Etroplus suratensis is listed as "decreasing" by IUCN.

Major Threats:
A major threat to Etroplus suratensis is pollution, habitat destruction, land reclamation, and exploitation for food and commercial interests.
Another threat is due to introduction from exotic species like Oreochromis mossambicus, Trichogaster trichopterus (Kurup 2007; Krishnakumar et al 2009).
There have also been reports in the past, of the Epizootic Ulcerative Syndrome (EUS) disease outbreak, which has spread in South and southeast Asia since 1980 (Pathiratne & Rajapakshe 1998).

Conservation Actions:
Despite the species being in high demand, the wild populations of the species have not been given sufficient conservation attention.
There have been attempts in the past to create 'no fishing zones' within some of the larger estuaries and the species did seek refuge in these protected zones. Such No-fishing zones should be extrapolated to other regions as well, to guarantee effective genetic preservation.
This is declared as the state fish by the government of Kerala.
Captive breeding has been undertaken by Padmakumar et al. (2004).
An aquatic sanctuary was made in Vembanad Lake for this species.
The Vembanad lake protection forums has started 'Matsyatavalam' (home of fishes) for the sustainable fisheries of this species.
Cage culture of this species is being practiced in Vembanad Lake and Vypin Islands.



Tank Size and setup:


Etroplus suratensis can grow up to 16 " and requires a large tank.
A minimum tank of about 500 liters should be set up for these cichlids.
The tank setup should imitate a river flowing stream or river bed, with gravel of multiple size, small rounded boulders, driftwood can be added to simulate roots of trees.

Water Parameters: Etroplus suratensis are a brackish water fish.
A ph range of 8-9 and Gh range from 10-25 can be maintained for these fish.
They are intolerant of nitrates hence a very good filteration is required to keep nitrates very low and good oxygenation in water.



Tank Mates:


Etroplus suratensis form loose groups in wild .
A minimum group of 6-8 is recommended, in smaller groups the weaker specimens will be picked upon.
A dominancy hierarchy will be established by the time they reach maturity.
Other tank mates can be cyprinids like Danio, Devario, Rasbora spp. can be used.
They are not aggressive cichlid so should not be kept with other fish or cichlids which are aggressive in nature.


Sexual Dimorphism & Breeding:


There are no obvious external sex differences in fin length or intensity of colour pattern.
Males tend to be larger than females.
The genital papillae in males is longer and more pointed than of females in which it is broader and rounder.
During breeding colour's of both sex become more intense and black stripes are seen near eyes.

Breeding Etroplus suratensis is a bi parental substrate spawner, however they are not monogamous, i.e a permanent pairing does not take place.
Weak temporary bonds are formed during mating and brood care.
Observations is wild have seen them breeding in two seasons, dry monsoon period ( December to april) and monsoon ( June to September).

A breeding site is selected and surrounding area is defended against intruders.
Eggs are normally deposited in a sheltered position on the side or top of rock and are attached by short filaments.
The eggs are defended by both parents.
Eggs hatch after 2 days at temperature of about 26 C. Fry are moved to pre excavated nursery pits by parents un till their egg yolks are absorbed.
Fry are free swimming in further 2-3 days, they may also remain with their parents and feed on mucus on the body of parents.
This parental care can be extended till fry are about 30 -40 mm in size.

Eggs can also be removed after they are deposited, as the parents or other fish can eat them. if this is done the rock with eggs should be removed, water from parents tank should be used.
Water flow across eggs can be simulated by using a air line close to rock.
Once fry are free swimming they can be fed armetia.



Species Snapshot

Species Card


Particulars Details
Scientific Name Etroplus suratensis
Common Name Green Chromide, Karimeen
Genus Etroplus
Subfamily Etroplinae
Geographical Origin Asia:Western Indian Ocean: India and Sri Lanka.
Diet Omnivorous, herbivorous
Gender Differences Mono morphic
Breeding Substrate Spawner
Temperament Peaceful
Con Specific Temperament Mildly aggressive
Water hardness Brackish water; ph range : 8-9, dh range: 9-19
Difficulty Level in Aquariums 2


Morphometric Data


Particulars Details
Total Length(inches) 8.00
Standard Length(inches) 6.50

Measurements as % of Total Length


Particulars Details
Body Depth 55.30 %
Head length 31.60 %
Pre Dorsal length 34.80 %
Pre Pectoral length 30.90 %
Pre Anal length 50.00 %
Pre Pelvic length 30.80 %
Caudal Peduncle Depth  %
Caudal Peduncle Length  %
Fork length  %
Length of Last Dorsal Fin Spine  %
Pectoral Fin Length  %
Pelvic Fin Length  %

Measurements as % of Head Length


Particulars Details
Head Width  %
Snout length  %
Eye diameter 28.06 %
Pre Orbital Length 29.40 %
Inter Orbital Width  %
Pre Orbital Depth 29.40 %



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