BOMBAY DUCK -Harpodon nehereus (Hamilton, 1822) – Guest Article

Bombay duck is not a duck but a fish consumed as a delicacy in Maharashtra. How did its name from Bombil became Bomaby duck? Read on to know more..

Source: BOMBAY DUCK -Harpodon nehereus (Hamilton, 1822) – Guest Article

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BOMBAY DUCK –Harpodon nehereus (Hamilton, 1822) – Guest Article

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Fresh catch of Bombay duck Harpodon nehereus

If you have ever get a chance to visit Mumbai, I am sure you will notice the word “Bombil fry” (Bombil is the Marathi name of Bombay Duck fish) in the menu card of any hotel, as it is the iconic fish species of Mumbai. Being the third most dominant fishery of India next to Oil sardine and Mackerel fishery, the single species Harpadon nehereus contributes to an estimated catch of 112646 tonnes (i.e.) 3% of the total marine fish landing of India (CMFRI Annual Report – 2014-15).

WHY THE NAME BOMBAY DUCK?

The name has nothing to do with ducks. During the British Raj the Europeans could not stand the smell of the fish drying in the sun. It reminded them of the odor of the wooden railroad cars of the Bombay Mail train, which turned musty and pungent during the monsoon. The Hindi word for mail is “dak”, hence the name Bombay-Dak, or Bombay-Duck.”.

This fish has a semi-transparent appearance with compressed and elongated body, extended lower jaw; the most prominent key character is the extension of the lateral line up to the pointed median lobe of the caudal fin. Being a carnivore with voracious feeding nature, gut content analysis reveals that, small fishes like unicorn cod, anchovies and shrimps (Acetes sp.) are the major food items. Cannibalistic behaviour is also noticed in Bombay duck.

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DISCONTINUOUS DISTRIBUTION

Though this fish is significant in the Indian fishery, it has a discontinuous distribution pattern restricted between the northern latitude of 180 N and 220 N (North West coast – Gujarat, Maharashtra and North East coast – West Bengal, Odisha) and nearly 90% of the Bombay Duck landing is mainly from the North West coast of India. The characteristic tidal amplitude in this Northern latitude of the Indian coast is the prime reason for this discontinuous distribution. The tidal oscillation in this region is associated with abundance of shrimps and anchovies making it easy and less demanding for foraging of Bombay Duck.

Bombay duck is caught by the Dol net (a type of bag net) and the operation of this gear depends on the strong tidal current at depth ranging from 20-30 m. The fish is consumed mainly as fresh form and the scaffold dried or laminated Bombay duck is consumed locally and exported to other countries like Mauritius, Sri Lanka etc.

TAXONOMIC POSITION

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Superclass: Gnathostomata

Class: Actinopteri

Order: Aulopiformes

Family: Synodontidae

Genus: Harpodon

Species: H. nehereus

Author: (Hamilton, 1822)

IUCN Status: Not Assessed (NA)

Kantharajan Ganesan is a Post Graduate student at the Aquatic Environment & Health Division,  Central Institute of Fisheries Education (CIFE), Versova, Andheri West, Mumbai, Maharashtra, India

© Deepak Samuel – January, 2016

Non-prevalence of mud crab hatcheries in India: A matter of concern – GUEST (OPINION) ARTICLE

MUD CRAB

MUD CRAB

The mud crabs (Scylla spp.) are fast growing species that attains larger size among portunid crabs and widely distributed throughout the coastal zones of Indo-West Pacific region. They represent as a valuable component of traditional, small scale coastal fisheries in many countries of tropical and subtropical Southeast Asia which stands as a significant commodity that fetch high price in the international seafood market. They have winsome qualities such as faster growth, larger size, high reproduction capacity (fecundity), disease resistance, live marketability, adaptability to farming systems etc.

In India, the market demand for mud crab is satisfied mainly from capture fisheries. I believe that there is only one commercial hatchery in India (Rajiv Gandhi Centre for Aquaculture (RGCA), Sirkali, Tamil Nadu, India) under the Marine Product Export Developmental Authority (MPEDA) where, the production of seed does not meet the demand. As a result, the mud crabs are heavily fished in the wild. Over the last three decades, exploitation of mud crab populations has increased tremendously in many countries in South East Asia. In addition to paramount fishing pressure, loss of mangrove habitats, irrational fishing of gravid females and undersized crabs, collection of wild seeds for grow out practices etc. paved way to the tremendous decline of mud crab resources in the wild. This is evident from the declining crab landings and higher occurrence of small sized crabs over the last two decades.

It is high time that the aquaculturists should focus on establishment of mud crab hatcheries like that of the existing shrimp hatcheries. At the same time, there is an urgent need for ecological and stringent management action that aims to keep the fishing practices of mud crabs at sustainable levels. In some countries, like Australia, a minimum legal landing size for mud crabs has been prescribed and strictly adhered to. If the present rate of exploitation continues, it will lead to commercial extinction of mud crabs in the near future. All said and done, the possibility, feasibility and production of mud crab hatcheries should be carefully considered before venturing in.

About the contributor:  Dr Vishwanathan is a crustacean biologist and taxonomist, specializing on marine crabs. He is currently working as a Research Associate at the National Centre for Sustainable Coastal Management (NCSCM), Chennai. 

© Deepak Samuel, August 2015

THRUSH COWRIE – Erosaria turdus (Lamarck, 1810)

The thrush cowrie Erosaria turdus in full glory

The thrush cowrie Erosaria turdus in full glory

The name ‘thrush’ for this species of cowrie is related to the spots as seen on the bird wood thrush (Hylocichla mustelina), a small or medium-sized songbird, typically having a brown back, spotted breast, and loud song. The thrush cowrie Erosaria turdus (Lamarck, 1810) is an extremely variable species common in the Red Sea, Oman, the Persian Gulf and western India, East Africa (Comores, Kenya, Madagascar, Mozambique, Oman, Somalia, Tanzania), in the East Coast of South Africa and – as a non-indigenous species – in European waters and in the Mediterranean Sea (Lampedusa, Israel, Djerba Island in Tunisia, Libya, Egypt), where it has been introduced through the Suez Canal (Heiman, 2002).

The brown spots on the breast of a wood thrush

The brown spots on the breast of a wood thrush

Thrush cowries inhabit the intertidal regions of reef areas in shallow waters at 2-10 meters depth, observed usually grazing on algal beds, on reef flats or sandy, muddy seabed. It reaches an average size of 3-4 cm in length and is quite variable in pattern and colour. Populations of the species in the Gulf of Aqaba can be distinguished as a subspecies Erosaria turdus pardalina (Dunker, 1852) and these shells differ by having a larger shell with mostly elongated extremities (Heiman and Singer, 2008).

Erosaria turdus has a more or less oval shape with the dorsum surface being smooth and shiny, purely because of the constant bathing of mantle from inside the animal. White being the base, colour varies from yellowish to greenish with small brown spots (like that of the wood thrush bird) scattered all over, becoming larger on the sides. The margins are white, sometimes light pink or even with small brown marks in the middle. The aperture view reveals a light purplish colour inside the shell. The mantle is brownish in colour with branched structures of the papillae while the periphery of the mantle is bordered with coffee brown colour.

This image was clicked in the intertidal reef area of Shivrajpur, Gulf of Kutch, Gujarat moving over a muddy substratum. It is a common species along the Gujarat coast, Tamil Nadu, Lakshadweep and Andaman & Nicobar islands of India.

Taxonomic position

Kingdom: Animalia

Phylum: Mollusca

Class: Gastropoda

Subclass: Caenogastropoda

Order: Littorinimorpha

Superfamily: Cypraeoidea

Family: Cypraeidae

Genus: Erosaria

Species: E. turdus

Author: (Lamarck, 1810)

IUCN Status

Not Assessed (NA)

References

Heiman EL & A Singer. 2008. New pink form of Erosaria turdus pardalina (Dunker, 1852). Triton No. 17 p. 25.

Heiman EL. 2002. Cowries of East Sinai. Published privately. 208 pp.

https://www.audubon.org/field-guide/bird/wood-thrush – the wood thrush

 

©Deepak Samuel, July 2015

Guest Article – ECHINODERMS PREVENT GLOBAL WARMING!

Yes! Though echinoderms seem insignificant when compared to dolphins and sharks, they too have been secretly doing their part to save the planet!

Echinoderms are exclusively marine organisms with a few exceptions among ophiuroids (Talbot & Lawrence, 2002). After the last Permo- Triassic extinction event only five groups survived. They comprise of Echinoids (Sea urchins, Sand dollars and Heart urchins), Asteroids (Sea stars), Ophiuroids (Brittle stars and Basket stars), Crinoids (sea lilies and feather stars) and Holothurians (Sea cucumbers).

A yellow sea lily on a hard substrata, Andaman

A yellow sea lily on a hard substrata, Andaman

These organisms have complex skeletons made up of high Mg calcite called STEREOM, which is highly porous and light in weight. The echinoderms fix carbon by fixing carbonates to build their shells from carbon fixed at the sea surface by floating phytoplankton that utilize carbon for producing energy through photosynthesis. These carbonates later get fixed as sediment once the echinoderms die and remain in a fixed state due to the stability of Stereom. According to Dr Mario Lebrato, echinoderms deliver more carbon to sediment than foraminiferan’s do. He and his team estimated that more than over a tenth of a gigatonne of carbon a year was fixed by echinoderms.

A sea lily curled up on a rope at a wreck site, Chidiyatapu, Port Blair, Andaman

A sea lily curled up on a rope at a wreck site, Chidiyatapu, Port Blair, Andaman

Echinoderms, as benthic organisms involve themselves in a dynamic process where they fix carbonate compounds obtained from phytoplankton that utilize carbon in photosynthetic processes. Echinoderms surprisingly contribute more than hundred thousand million kilograms of carbon in the form of carbonates fixed in the sea (Lebrato et al. Global contribution of echinoderms to the marine carbon cycle: a reassessment of oceanic CaCO3 budget and the benthic compartments.

How much do we do towards slowing down global warming?

References:

Dr Mario Lebarto: Is an ocean acidification expert at the Scripps Institution of Oceanography.

Talbot TD and JM Lawrence. 2002. The effect of salinity on respiration, excretion, regeneration and production in Ophiophragmus filograneus (Echinodermata: Ophiuroidea). Journal of Experimental Marine Biology and Ecology 275:1-12.

 

Mario Lebrato et al.  2010. ,Global contribution of echinoderms to the marine carbon cycle:CaCO3  budget and benthic compartments, University of Southampton, School of Ocean and Earth Science, National oceanography Center, UK. Ecological Monographs, 80 (3), pp.441-467. doi :10.1890/90-0553

 

This guest article is written by NINA TABITHA SIMON, a PADI certified Dive Master and currently working as a Junior Research Fellow at the National Centre for Sustainable Coastal Development, Chennai, India

 

Image © Karan Baath

 

© Deepak Samuel, October 2014

SPINELESS CUTTLEFISH – Sepiella inermis (Van Hasslet, 1835)

Spineless cuttlefish just harvested with the help of a jig

Spineless cuttlefish just harvested with the help of a jig

Sepiella inermis, the Spineless cuttlefish is one among the three known spineless cuttlefish of the world (others being S. japonica and S. ornata). This species forms a commercially important fishery in India besides Thailand and Sri Lanka. Absence of spine in the cuttlebone at the posterior end distinguishes this species from other cuttlefish. Presence of a glandular pore at the posterior end of the mantle is the second important morphological feature to differentiate this species from the rest. About 16-20 iridescent spots are evenly distributed along the mantle fin margin.

Spineless cuttlefish is a demersal, shallow water species inhabiting depths up to 40 m distributed in the Indo-Pacific, Red Sea, Gulf of Aden to Andaman Sea and southern South China Sea.

The spineless cuttlefish is a small species growing to a maximum size of 12.5 cms. Males are smaller than females and exhibit dark colouration of the body during mating.  Females have paler colouration and submit calmly to dominant males. The mating begins after the males start to involve in ‘arm-touch’ and by swimming adjacent to the females. The arms are then interlocked for 2 – 4 minutes. Males die a few days after the process of mating and the female’s dies after depositing the eggs. Eggs laid by the spineless cuttlefish are grape-like, black in colour and are laid in clusters by the females. Eggs range between 220-500 numbers per deposit laid on any hard substrata like discarded nets, seaweeds etc.

The hatchlings (also called as ‘paralarva’) of spineless cuttlefish hatch out after an incubation period of 18-21 days (This took place in the laboratory condition when I personally carried out research). The paralarva measure 7.5 mm (average) in size and are planktonic in nature, swimming in a slanting position. Right from the time of hatching the paralarvae start hunting for their prey like larval shrimps or copepods.

The population of spineless cuttlefish has been found to dwindle in India as many reports suggest due to overexploitation. This species has been successfully raised in aquaculture and has the potential for future commercial development.

Taxonomic Status

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Subclass: Coleoidea

Superorder: Decapodiformes

Order: Sepiida

Family: Sepiidae

Genus: Sepiella

Species: S. inermis

Author: (Van Hasslet, 1835)

IUCN Status

Data Deficient (DD)

©Deepak Samuel, August 2014

SAILORS OF SEA – Velella velella (Linnaeus, 1758) – GUEST CONTRIBUTION

Sailor of the sea washed ashore Manadhoo island, Maldives

Sailor of the sea washed ashore Manadhoo island, Maldives

Sailors of the sea are named aptly because of their drifting movements along with water currents. A tiny free floating organism, V. vellala lives in air-sea interface of ocean categorized under a planktonic group called pleuston (animal that lives partly outside and under water). Though more than 25 synonyms exist for this species, it is one and the same. These creatures are found drifting in the sea and can attain a maximum size of 7cm in size.

Sailors of the sea are deep blue in colour with transparent oval shape floats and tentacles beneath it. The float consists of an air sealed sac for maintaining buoyancy. The reason behind the name is they have a small triangular stiff sail formed of chitin that is present vertically at the float. This runs diagonally and functions for sailing. These small creatures are distributed in tropical and other warm water regions.

The small triangular stiff sail in Velella  velella uses wind for movement and direction in water. It has other names that includes purple sail, wind sailor, sea raft etc. Earlier sailors of the sea was classified under group with special free floating community shiphonophores (tube bearing) and thought to be a colonial hydrozoa with single feeding polyp in the centre, surrounded by a group of reproductive polyps (Gonozooids).

Recent studies proved that it is a highly modified single hydroid polyp and classified them under chondrophore. Polyp produces medusa that releases by budding planula larvae. The offspring shows polymorphism (difference in morphology) with difference in sail orientation. Orientation of the sails defines the direction of the animal and the shore it strands. Though it is tiny, it is carnivore in nature (primarily plankton). The tentacles present under water have a specialized type of stings known as nematocysts or cnidocysts. The nematocysts consist of toxin that is used to feed on plankton. Even though these creatures are carnivores, they are preyed upon by the shell less mollusc nudibranchs (Secondary carnivore). The toxin of Velella doesn’t hurt nudibranchs, because they are stored in their sacs (cnidosacs). These toxins are used further for hunting prey or for defense. Since, these nematocysts can’t penetrate human skin it is harmless.

 

Taxonomic position

Kingdom: Animalia

Phylum: Cnidaria

Class: Hydrozoa

Subclass: Hydroidolina

Order: Anthoathecata

Suborder: Capitata

Family: Porpitidae

Genus: Velella

Species:V. velella

 

This guest article is contributed by UMER KHALIFA who works in the Maldivian island of Manadhoo, Noonu atoll.

© Deepak Samuel, July 2014

 

PAPER BUBBLE SHELL – Hydatina zonata (Lightfoot, 1786)

Dorsal and ventral view of the paper bubble shell Hydatina zonata. The ventral view gives a clear understanding of the colour pattern on the mantle.

Dorsal and ventral view of the paper bubble shell Hydatina zonata. The ventral view gives a clear understanding of the colour pattern on the mantle.

Bubble prints are made by preparing colouring bubble solution and blowing the bubbles. A paper is pressed on to the created bubbles to produce beautiful bubble pictures. More unlikely, a paper bubble shell is rightly named so for the thin, translucent shell it possesses. Also called as zoned paper shell it is characterized by strongly inflated cream shell with wide spiral brown bands. The spiral bands are around the base and at the apex (the top or highest part of something, especially one forming a point) of the shell, where the brown lines are absent.

The inner soft part of the paper bubble shell is lovely to look at. The colour of the soft parts called the mantle (The mantle (also known by the Latin word pallium meaning mantle, robe or cloak) is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself). This varies from a pale translucent white colour to a dark pinkish brown bordered with white undulated pattern.

Paper bubble shells can reach a maximum of 40 mm length. They are distributed in tropical Indo-pacific regions. I collected the sample from trash which was being sorted out to be sent to poultry feed industries at Mandapam fish landing centre, Palk bay, South east coast of India. While scientific records give us insight that this species is collected from depths of 30 – 60 m, conversation with fishermen reveal that they are even found at depths ranging from 10-15 mts.

Not much is known about the paper bubble shell and this provides a good opportunity for researchers to carry out research work on this particular species for its biology. Though considered to be rare, landing of this shell is common along the Gulf of Mannar and Palk Bay regions of India.

Taxonomic position

Kingdom: Animalia

Phylum: Mollusca

Class: Gastropoda

Subclass: Heterobranchia

Superfamily: Acetonoidea

Family: Aplustridae

Genus: Hydatina

Species: H. zonata

Author: (Lightfoot, 1786)

IUCN Status

Not Assessed (NA)

 

©Deepak Samuel, July 2014

GOOD CATCH OF MULLETS – Parangipettai landing centre

Mullets ready for sale

Mullets ready for sale

SNAKE WITH YELLOW LIPSTICK? – Laticauda colubrina the yellow-lipped sea krait

Yellow-lipped sea krait Laticauda colubrina dead and washed ashore @  Havelock beach, Andaman; insert - closer look at the head

Yellow-lipped sea krait Laticauda colubrina dead and washed ashore @ Havelock beach, Andaman; insert – closer look at the head with yellow lip

The yellow-lipped sea krait (Laticauda colubrina) is a reef dwelling species belonging to the family Elapidae (some researchers place them in family Hydrophiidae). It is also called as banded sea krait. They are often noticed by divers in seas around coral reefs and rocky shores. It is named so because of their yellow upper lip. It is a very common species in the eastern Indian Ocean distributed along the eastern coast of India through coasts of south East Asia, Malay Archipelago, southern China, Taiwan and the Ryukyu islands of Japan.

The yellow-lipped sea krait is light to dark bluish grey above with yellowish underside. Black bands are more or less uniform in width, narrowing down on the belly. Snout is yellow that extends backward on each side of the head in a black backdrop.

Nocturnal hunting among the reefs and coral rubble is a characteristic behaviour of yellow-lipped sea kraits. They are often involved in group hunting (co-operative hunting technique) feeding on fishes hiding in the crevices. Eels are one of their favourite food and the snakes flushes the eels out of their hideouts and then feed.

They are venomous but are not aggressive to divers (there are few recorded incidents where fishermen have been bitten while clearing their nets of trash or debris). The krait has highly toxic venom that can cause death to humans. It does not bite unless it is being provoked.

Yellow-lipped sea krait males measure about 87 cm and are smaller than females which measure about 142 cm. The paddle shaped tails measure 13 cm for males and about 15 cm for females.  The tail and the head of the yellow-lipped sea krait are similar in appearance. This is an adaptation to help to protect the snake from its predators. When the snakes probe for food in crevices with their head, they are unable to observe approaching predators. Since the lateral aspect of tail corresponds to the dorsal view of the head in addition to tail movements, the snakes fool their potential enemies easily.

The yellow-lipped sea kraits have large ventral scales that provide excellent traction when they crawl on land thereby making it easy for them to move about in sandy shores. This helps them drink freshwater periodically when they come to land. They also mate in the land and large numbers aggregate along sandy shores during breeding seasons. A female can lay up to 20 eggs in a clutch (eggs laid in a single time).

 

Taxonomic status

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Superclass: Gnathostomata?

Superclass: Tetrapoda?

Class: Reptilia?

Order: Squamata?

Suborder: Serpentes?

Infraorder: Alethiophida?

Family: Elapidae?

Subfamily: Laticaudinae?

Genus: Laticauda

Species: L.colubrina

Author: (Schneider, 1799)

IUCN Status

Least Concern (LC)

Identified by:  Dr Aaron Savio Lobo

©Deepak Samuel, June 2014