Etroplus canarensis DAY, 1877

Canara Pearlspot Cichlid

Etymology

Etroplus: from the Ancient Greek ἦτρον (etron), meaning ‘belly, lower abdomen’, and ὅπλον (hoplon), meaning ‘weapon, armour’, in reference to the prominent spinous anal-fin rays in members of the genus.

canarensis: named for South Canara district in the state of Mysore, southwestern India, corresponding to modern day Dakshina Kannada district in Karnataka state.

Classification

Order: Perciformes Family: Cichlidae

Distribution

Appears locally endemic to southern Karnataka state, southwestern India where it’s known only from the Kumaradhara-Netravati river system.

It can be found in both the Kumaradhara and Netravati although it was thought to be restricted to the former for a number of years.

Type locality is ‘South Canara, India’, although it apparently relates to a spot close to Uppnangudi where the Kumaradhara and Netravati merge.

The two rivers are under a degree of threat from agriculatural pollution, sand mining and other human activities.

Habitat

This species occurs exclusively in oxygen-rich fresh water with the downstream limit of its range appearing to be approximately 50 km from the mouth of the Netravati, below which point it is replaced by the euryhaline congeners E. maculatus and E. suratensis.

Its habitats are highly-seasonal in nature with annual monsoons bringing about severe increases in water depth, flow-rate and turbidity.

At one locality in the Netravati River the water was quite clear and flowing gently over a rocky substrate during the dry season.

Altitude was around 140 m AMSL, pH 6.5, tds 50 ppm, conductivity 94 µS, GH 2.0 and KH 2.0 with a temperature of 32.6 °C/90.68 °F at midday.

Sympatric fish species included Puntius mahecola, Haludaria fasciata, Garra mullya, Mesonoemacheilus triangularis, Devario malabaricus, Esomus danricus, Parambassis wolffii, Carinotetraodon travancoricus, Rasbora daniconius, Barilius gatensis, Hypselobarbus jerdoni, and Hyporhamphus limbatus.

In the Kumaradhara basin it was recorded at a spot where altitude was 150 m AMSL, pH 6.5, tds 40 ppm, conductivity 85 µS, GH 2.0 and KH 2.0 with a temperature of 33.1 °C/91.58 °F at 1800 h.

The substrate was mainly composed of small rocks and leaf litter with some tree roots projecting into the water along one margin while other fishes included Puntius mahecola, Pristolepis marginata, Garra mullya, Devario malabaricus, Carinotetraodon travancoricus, Rasbora daniconius, and Barilius gatensis.

Maximum Standard Length

100 – 110 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions of 120 ∗ 45 cm or equivalent should be the smallest considered for long-term care.

Maintenance

Should ideally be maintained in an aquarium set up to resemble a flowing stream or river with a substrate of variably-sized, water-worn rocks, sand, fine gravel and perhaps some small boulders.

This can be further furnished with driftwood roots or branches, and while the majority of aquatic plants are likely to be eaten by the fish hardy types such as Microsorum or Anubias spp. may survive attached to the décor.

This species is intolerant to accumulation of organic pollutants and requires spotless water meaning weekly water changes of 30-50% volume should be considered routine.

Strong water flow is unnecessary but a relatively high ratio of dissolved oxygen is essential.

Water Conditions

Temperature: 22 – 32 °C; a value around the middle of this range is suggested for general care although a degree of seasonal variation is advisable (see ‘Reproduction’).

pH: 6.0 – 7.5

Hardness: 18 – 179 ppm

Diet

Observations of wild fish suggest it to be something of a generalist with a tendency to graze aufwuchs and filamentous algae from solid surfaces.

In the aquarium it can be offered high quality prepared foods but displays a preference for small live or frozen items such as chironomid larvae (bloodworm), Tubifex, Artemia, mosquito larvae, etc.

At least some of the dried products should contain a significant proportion of vegetable matter such as Spirulina or similar, while chopped peas and suchlike are also useful supplements.

Behaviour and CompatibilityTop ↑

Unless breeding this species is relatively peaceful and will not predate on any but the smallest fishes.

Pelagic cyprinids which occur alongside it in the wild such as Dawkinsia spp., Devario malabaricus or Rasbora daniconius are particularly suitable tankmates although if geography isn’t an issue it should also do well alongside many tetras, for example.

Best avoided are territorial or otherwise aggressive species and those that require harder water, while other cichlids should also be omitted.

Etroplus species are loosely gregarious and tends to form groups unless spawning with juveniles in particular displaying a strong social response when threatened.

A group of 8+ individuals should therefore be the minimum purchase and these will form a noticeable dominance hierarchy once sexual maturity is reached.

When maintained in smaller numbers weaker specimens can become the target of excessive abuse by dominant individuals or the group may fail to settle and behave nervously.

Sexual Dimorphism

Adult males tend to be a little larger and slightly heavier in build than females.

Reproduction

This species is a biparental substrate spawner which forms weak, temporary pair bonds during the reproductive period.

Sexual maturity appears to be reached at around 24 months of age so a degree of patience will be required if young specimens are purchased.

In nature the fish are thought to breed during the months of December and January, when temperatures are cooler and high monsoon waters have receded, and simulation of the change between these seasons can sometimes induce captive examples to spawn.

This can be achieved via a period of keeping the fish at a stable temperature towards the upper end of the range suggested above followed by several daily changes of 20-25 % tank volume using cooler water.

Nuptial individuals display a change in colour pattern in which the dark vertical body bars are replaced by a solid dark patch and vertical bars appear on the front of the head.

During courtship a particular site is selected and the surrounding area defended against intruders until the pair is ready to spawn.

Eggs are normally deposited in a sheltered position on the side or top of a rock to which they are attached by short filaments.

Post-spawning both parents continue to defend the site although the male may spawn with other females if available.

Incubation is approximately 4 days at a temperature of 26.7 °C/80.0 °F with the fry swimming freely in a further 2-3 days.

The majority of breeders prefer to remove the eggs prior to hatching as they ‘re often eaten by tankmates or the parents themselves, with the most common method being to remove the rock with eggs attached and place it in a separate container with water from the adults’ tank.

Water movement across the eggs is maintained by placing an air-line or filter outlet close to the rock while any displaying signs of fungus should be removed as they’re noticed.

Once free-swimming the fry are large enough to accept Artemia nauplii and similar immediately.

NotesTop ↑

E. canarensis is also known as the banded chromide or ‘roman numeral’ cichlid in the aquarium hobby.

There have been concerns over its natural status due to unmanaged collection for the trade but it is now bred commercially in Southeast Asia which has helped reduce the pressure on wild stocks.

Etroplus is the only cichlid genus native to the Indian subcontinent and Sri Lanka and currently comprises three species among which E. canarensis is uniquely limited to freshwater and restricted in range.

Its congeners E. maculatus and E. suratensis are both euryhaline inhabiting estuaries, coastal lagoons and the lower reaches of rivers around coastlines of western and southern India plus northern Sri Lanka.

E. maculatus can easily be told apart from the others since dark markings on the body are reduced to 1-3 dark blotches just above midbody (unless stressed when short bars may appear in the upper portion of the body with a solid dark posteroventral patch) and is much paler overall, with the majority of body scales having an orange-red centre.

The remaining species both possess a series of normally 6 dark vertical bars on the body (excluding those on the head and caudal peduncle) but in E. canarensis the anterior 3 bars tend to bifurcate as the fish mature, base body colour is buff-grey, and some body scales have a yellowish central patch, whereas in E. suratensis the bars remain solid throughout life, base body colour is greenish-brown, and numerous body scales have a pearly-white central spot.

E. suratensis is also much the larger fish and capable of exceeding 300 mm SL.

Its closest relative among other cichlids is the Malagasy endemic genus Paretroplus and these two are sometimes grouped together under the putative subfamily Etroplinae.

They are an ancient, morphologically distinct lineage and represent the evolutionary sister group to all other cichlids (Sparks and Smith, 2004) with several unique specialised characters (Sparks, 2001; Stiassny et al., 2001).

These include complex paired anterior swim bladder chambers that are located within enlarged exoccipital recesses forming a direct otophysic (mechanical) connection between the gas bladder and inner ear, highly modified supraoccipital and exocippital bones of the neurocranium, and specialized ligaments associated with the suspensorium and oral jaws.

Etroplus can be told apart from Paretroplus by a number of characters including: possession of tricuspid (vs. unicuspid in Paretroplus) teeth; teeth present in multiple rows in both upper and lower jaws (vs. a single row of teeth in upper and lower jaws; teeth numerous in both upper and lower jaws (vs.  teeth few in number (< 18 in upper jaw, < 14 in lower); paired anterior gas bladder extensions rather typical and tubelike (vs. paired anterior gas bladder extensions highly-modified with  multiple anterior polyplike chambers possessing a tough and thickened tunica externa, and extremely narrow connections (diverticula) to the main gas bladder chamber); an elevated number of anal-fin spines; configuration of the anal-fin pterygiophore ⁄hemal spine complex (Sparks, 2001; Stiassny et al., 2001).

References

1. Day, F., 1877 - William Dawson & Sons, London: 369-552
   The fishes of India; being a natural history of the fishes known to inhabit the seas and fresh waters of India, Burma, and Ceylon. Part 3.
2. Cuvier, G. and A. Valenciennes, 1830 - Histoire naturelle des poissons v. 5: i-xxviii + 1-499 + 4 pp.
   Tome cinquième. Livre cinquième. Des Sciénoïdes.
3. Sparks, J. S., 2008 - Bulletin of the American Museum of Natural History 314: 1-151
   Phylogeny of the cichlid subfamily Etroplinae and taxonomic revision of the Malagasy cichlid genus Paretroplus (Teleostei, Cichlidae).
4. Sparks, J. S. and R. C. Schelly, 2011 - Zootaxa 2768: 55-68
   A new species of Paretroplus (Teleostei: Cichlidae: Etroplinae) from northeastern Madagascar, with a phylogeny and revised diagnosis for the P. damii clade.
5. Sparks, J. S., and W. L. Smith, 2004 - Cladistics 20: 501-517
   Phylogeny and biogeography of cichlid fishes (Teleostei: Perciformes: Cichlidae).
6. Subramanian, M., 2005 - World Wide Web electronic publication, www.indianaquariumhobbyist.com: Accessed on 25.10.2013
   Seeking the Elusive Etroplus canarensis.