FISH
- THE ‘FISH’ [ = ‘Pisces’ in Latin; ‘Poisson’ in
French; ‘Piscado’ in Spanish; ‘Pisce’ in
Italian; ‘Fisch’ in German; ‘Machli’ in Hindi;
‘Matsya’ in Sanskrit etc.]:
Fishes are a quite diverse
heterogeneous assemblage and exhibit a phylogenetic continuity. To most
biologists, the term ‘fish’ is not so much a taxonomic ranking as a
convenient description for aquatic organisms as diverse as hagfishes, lampreys,
sharks, rays, lungfishes, sturgeons, gars and advanced ray-finned fishes.
Recognizing this diversity, fish has been defined as:
“a poikilothermic, aquatic
chordate with appendages (when present) developed as fins, whose chief
respiratory organs are gills and whose body is usually covered with scales”.[
TM Berra, 2001, Freshwater fish distribution.].
Some workers restrict the term ‘fish’
to only jawed bony fishes viz., Actinopterygii, Latimeriidae and Dipnoi.
Some also prefer to include sharks, rays and their relatives (because some
sharks have the term ‘fish’ in their common name e.g., ‘dogfish’). Similar is
the case with jawless Hagfishes and Lampreys. Nelson (2006) used this term as a
matter of convenience, essentially to describe those vertebrates studied by Ichthyologists.
Despite their diversity, ‘fishes’ have been defined
(artificially) as:
‘aquatic vertebrates that have gills throughout life
and limbs if any in the shape of fins’.
- ‘FISHES’
vs. ‘FISH’:
The term ‘fishes’ is used when referring to individuals of more
than one species e.g., 100 individuals including those of Labeo
rohita, Catla catla and Cirrhinus mrigala will be correctly called as
‘fishes’.
The term ‘fish’ is
appropriately used when one is referring to one or more individuals of one
species e.g., 100 individuals of Labeo rohita as ‘fish’.
- FISHERIES
(Sing. – FISHERY):
Fisheries is a collective term where the cultivation and capture of
fish(es), Molluscans, Crustaceans, any other aquatic animal and even sea
weeds is included.
According to the Food and
Agriculture Organisation (FAO), US, a ‘Fishery’ is defined in
terms of the ‘people involved, species or type of fish, area of water or
seabed, method of fishing, class of boats, purpose of the activities or a
combination of the foregoing features’. This definition also includes a
combination of fish and fishermen of a region, the fishermen fishing for
similar species with similar gear types. A fishery may involve the capture of
wild fish or raising fish through fish farming or aquaculture.
As per the Dictionary, Fishery
(Sing.) / Fisheries (Plu.) include(s) the following:
The occupation, industry or season of taking fish or
other sea animals (as sponges, shrimp or seals).
- ICHTHYOLOGY
[Gk. Ichthys, a fish; logos or logy, a discourse):
A discipline of animal sciences involving all pure and applied aspects
of fish(es). - ICHTHYOLOGIST:
Basically, he/she is a student/professional of fish systematics, skilled
in constructing phylogenies and classifications. In addition he/she also
determines evolutionary trends based on comparative information from
morphological and other studies. On the whole, the scope of Ichthyology is
enormous and like any other allied disciplines, an Ichthyologist, too, is
concerned with exploring taxonomical, morphological, anatomical,
histological, physiological, embryological, ecological, genetical,
biotechnological, pathological, immunological, economical and other
applied aspects of fishes.
DIVERSITY:
·
NUMBER OF FISH:
Out of approximately 54,711 recognized living vertebrate species, fishes
constitute slightly more than one half of it. As will be evident from the
distributional diversity, the greatest number of fish species in the world
inhabits the Southeastern Asian region. It is worth mentioning here that in
contrast to Amphibians, Mammals and Reptiles, the known diversity of living
fishes exceeds that of known fossil taxa. Nelson (2006), based on
revisions, reports on new species, corrections and Web-based sources (like FishBase)
etc., reported an estimated 27, 977 valid species of fishes, belonging to 515
families. Out of 27,977, 108 are jawless fishes (70 Hagfishes and 38
Lampreys); 970 are cartilaginous Sharks (403), Skates and Rays (534) and
Chimaeras (33); and the remaining 26,000+ are bony fishes.
As per Fish Base (a
global information system about Fishes) November 2019 data there are
about 35315 species.
- HABITAT
DIVERSITY:
Fishes live in almost every type of aquatic habitat viz., fresh,
brackish or marine, from the tropics to the Polar Regions. Many freshwater
and marine species are also common in brackish water estuaries. About
one-third of families have at least one species with individuals that
spend at least part of their life in freshwater. About 12,000 species
(43%) of all species, live exclusively in freshwater lakes and rivers that
cover only 1 % of the earth’s surface and account for a little less than
0.01 % of its water (the mean depth of lakes is only a few meters). About
15,800 species live in oceans, which cover 70% of the earth’s surface and
account for 97% of its water with a mean depth of about 3,700 m.
Fishes are found to live up to an
elevation of 5,200 m in Tibet, where some Nemacheilines (Cobitidae)
live in hot springs. In the world’s highest (3,812 m) Lake Titicaca (South
America), a group of Cyprinodontids has undergone much radiation. Fishes also
live in the world’s deepest Baikal Lake (at least 1,000 m) and up to
7,000 m below the surface of the ocean. A few species make short excursions
onto land. Subterranean or hypogean fishes are found confined to total
darkness of caves or other underground areas or in the fast torrential
streams (= Hill Stream Fishes) of Tibet, China and India.
Oreochromis alcalicus
or Alcolapia alcalica (the soda Tilapia; Order Perciformes
or Cichliformes, Family Cichlidae) is endemic to hot soda Lake (hypersaline
lake), Magadi (Kenya) at temperatures as high as 42.5°C. At the
other extreme, Cod ice fishes, Trematomus (Order Perciformes,
Fam. Nototheniidae) live at about -1°- 4°C under the Antarctic ice
sheet, on account of producing antifreeze glycoproteins, preventing formation
of ice crystals in blood (hence often called cryopelagic). Many species
have acquired air-breathing organs, being essentially independent of
water for respiration and live in stagnant, tropical swamps (especially Lungfishes).
Lake-dwelling species may
show a preference for deep, cold, oligotrophic lakes or for shallower,
warmer and more productive mesotrophic and eutrophic lakes. In
lake waters they may show a preference for the open-water limnetic zone, the
benthic zone or shallow littoral zones. Stream fishes may prefer riffle
or quieter zones and a zonation of species is found from the headwaters to the
mouth of a river.
Some fishes also inhabit deep-sea
thermal vents in the eastern Pacific Ocean. In oceans, majority of fishes
are coastal or littoral. The animals living in the deep sea live under
extreme conditions of darkness, high pressure and temperature changes. The fish
life of the deep-sea habitat is among the most specialized of any habitats in
the world. The continental shelf at about 200 m depth has been
considered as a boundary between ‘shallow’ and ‘deep sea’. Most diverse
deep-sea assemblages occur between 40°N and 40°S latitudes. In general, any
species that is found at extreme ocean depths, more than 500 m and even beyond
8,000 m, is defined as a ‘deep-sea fish’, characterized by elongated to
dorso-ventrally flattened or eel-like body, large mouth, pointed fang-like
teeth, enlarged or minute eyes, bioluminescence etc. The fish in the
deep tend to be much smaller than on the surface, with minimal bone structure
and more jelly-like flesh. They are, therefore, slower and less agile than fish
living near the surface. They also tend to grow more slowly than surface fish.
Some take many years to reach sexual maturity. These adaptive features are,
obviously, the outcome of evolutionary adaptations to extreme pressure, cold
and darkness and such similarities among unrelated fishes are due to convergent
adaptations.
The upper 200 m of the open sea
is known as Epipelagic or Euphotic zone. There are three major
regions of ‘open water’ viz., Mesopelagic (200 – 1,000 m),
Bathypelagic (1,000 – 4,000 m) and Benthopelagic or Abyssopelagic
(4,000 – 6,000 m). The deep sea regions below 6,000 m are often referred as hadal
depths. The bottom-associated or benthic species swim just above the
bottom (= Benthopelagic) or live in contact with the bottom (= Benthic).
More than 1,000 species inhabit open waters of the deep-sea and another 1,000
species are benthic, with fairly good representation of Cartilaginous and bony
fishes.
- DISTRIBUTIONAL
DIVERSITY:
In both fresh and marine waters, the largest number of species occurs in
the tropics. The number is reduced towards Polar Regions. For the tropics
on one hand, a large number of freshwater fishes are found in tropical
Africa, southeastern Asia and the Amazon River, but on the other hand,
because of the characteristic physiographic and geological history,
relatively few freshwater species are found in Central America. Africa
exhibits the greatest diversity of non-ostariophysan (i.e., lacking
Weberian Ossicles) freshwater fishes but South America is poor on
this basis. Contrary to it, in temperate regions, Eastern North America
shows the greatest diversity of non-ostariophysan fishes. Most oceanic
islands and continental areas recently exposed from the last ice age
(e.g., northern regions of North America, Western Europe and Asia), lack
indigenous fishes confined to freshwater.
As far as the marine environment
is concerned, representatives of many marine genera and of some species occur
in the temperate and polar fauna of both hemispheres. The vast majority of
species, however, are tropical, most of the rest occurring only in the Northern
or only in the Southern Hemisphere.
About 130 marine species are
known to extend around the world in tropical or subtropical waters. The Indo-West
Pacific (Red Sea and Indian Ocean to Northern Australia and Polynesia) is
the richest, with most species occurring in New Guinea to Queensland. In
terms of diversity, Southeastern Africa and Queensland have the largest number
of marine shore fish. The West Indian or Caribbean fauna (southern Florida to
northern Brazil) is also appreciably rich. The West African marine fauna,
however, is relatively poor. Arctic and Antarctic faunas are depauperate i.e.,
lacking in numbers. In all, the greatest number of fish in the world inhabits
the southeastern Asian region.
- BIOGEOGRAPHICAL
DIVERSITY:
Biogeography is a new discipline that attempts to document and
understand spatial patterns of biodiversity. It is actually a
branch of ‘Physical Geography’, concerned with the present and past
distribution of animals and plants along with the examination of physical
environment affecting the distribution of a particular species across the
world. In other words, the science of biogeography attempts to document
the geographic distribution of taxa (i.e., descriptive
biogeography) and to explain their distributional patterns (i.e.,
interpretive biogeography). It is an active field of study in Ichthyology,
finding solutions to various problems related with the distribution of
fishes.
There are two approaches to
interpretive biogeography i.e., the ecological biogeography which
involves various environmental factors (viz., temperature, pH, dissolved
gases, turbidity, salinity, currents, competition etc.), limiting the
distribution of a species within a water body; and historical biogeography
which focuses on the origin of distributional patterns (i.e.,
paleontological studies or the study of fossils). Paleoclimatic changes
are often invoked in historical biogeography, especially when postulating that
discontinuous distributions result from dispersal events.
Dispersal and vicariant
events are two methods of distribution of fishes. Dispersal, active
or passive, is a movement to areas new to the existing population. Barriers of
varying effectiveness may be involved. It is of greatest biogeographic
significance if the breeding range of the species is increased. Vicariance,
on the other hand, is a process by which the geographical range of an
individual taxon or a whole biota is split into discontinuous parts by the
formation of a physical or biotic barrier to gene flow or dispersal e.g.,
through tectonic plates. Both dispersal and vicariant approaches are used to
explain disjunct or discontinuous distributions i.e., the
occurrence of a taxon in different areas with a marked geographical gap between
them e.g., Prosopium coulteri (Fam. Salmonidae) in western North America
and in lake Superior; Geotria australis (Fam. Petromyzontidae) in
Australia, New Zealand and South America etc. Further, Lungfishes found
distantly in Africa, South America and Australia are potential examples of vicariance,
suggesting that this group represents an ancient distribution limited to the
Mesozoic supercontinent Gondwana and the fossil record suggesting that
advanced lungfish had a widespread freshwater distribution and the current
distribution of modern lungfish species reflects extinction of many lineages.
MORPHOLOGICAL DIVERSITY:
SIZE
·
SMALLEST FISHES:
They all include Fishes from 4 Orders of Bony Fishes:
Order- Cypriniformes
o Paedocypris
progenetica [Images] (Fam. Cyprinidae, Subfamily – Rasborinae):
This translucent fish from Indonesia has been claimed not only the world’s
smallest fish (7.9 mm) but also the smallest vertebrate,
particularly before the description of the smallest
(7.7 mm) frog (Paedophryne amanuensis) in 2012 from Papua
New Guinea.
The
Ichthyologists, Maurice Kottelat from Switzerland and Tan Heok Hui
from the Raffles Museum of Biodiversity Research and National University
of Singapore discovered it in 1996 and described in 2006. The recorded
maximum size of 1.03 cm is in females whereas 0.98 cm in males. The
smallest known mature specimen was a female (0.79 mm), smaller than the
female of any other vertebrate species.
o Danionella
[Images] (Fam. Cyprinidae, Subfamily – Danioninae):
4 species of Danionella, lacking scales, barbels and lateral
line, are among other smallest cyprinids. The females of Danionella
translucida from lower Myanmar, ripe at 1.0 – 1.1 cm (longest about 1.2
cm).
Danionella
mirifica from upper Myanmar is slightly larger (1.4 cm). Danionella
dracula (1.0 – 1.2 cm; max. 1.7 cm), another species from Myanmar, is
unusual in having teeth made of bone, rather than the true teeth of
other fishes but the males have a pair of bony fangs, used for sparring
(fighting) with their mates. Danionella priapus (max.
1.6 cm) is endemic to India (West Bengal).
o Sundadanio
[Images] (Fam. Cyprinidae, Subfamily – Danioninae):
Still larger (about 2.3 cm in standard length), 8 sp. of Blue Neon Danio
(Sundadanio) are from freshwaters, peat swamps and blackwater streams of
Indonesia – Sumatra, Bangka and around the Anjungan and Kapuas drainage in
Borneo.
Order- Perciformes:
o Schindleria
brevipinguis [Images] (Stout Infantfish, Fam.
Schindleriidae):
Native to Australia’s Great Barrier Reef and Osprey Reef in the Coral Sea,
this species grows to a maximum total length of 8.4 mm, with males maturing at
about 7.0 mm.
o Trimmaton
nanus [Images] (Midget dwarfgoby, Fam. – Gobiidae):
Distributed in the Indian and the western Pacific Ocean, occasionally
found in outer reef areas and lagoons, up to a depth of 5.0 to 30 m,
it was the shortest known fish and vertebrate (1.0.cm) until 2004.
WORLD’S SMALLEST COMMERCIALLY HARVESTED FISH
o Mistichthys
luzonensis [Images] (Sinarapan, Fam. – Gobiidae):
Commonly named after a fishing gear, called ‘sarap’, having tiny
holes in the net, it was considered to be the world’s smallest commercially
harvested fish, found in the Lakes Bato and Buhi in Camarines Sur, Bicol
Region of the Philippines. It has been listed in the Guinness Book of
Records as the ‘smallest food fish’. The average length is about
1.25 cm, the males being smaller than females. Males (max. 1.35 cm) mature at
about 1.0 cm while females (max. 1.4 cm) at about 1.1 cm.
WORLD’S SMALLEST FISH BY MASS
o Pandaka
pygmaea [Images] (Dwarf pygmy goby, Fam. –
Gobiidae):
Found along the shady river banks in Rizal Province of Luzan
(Philippines), it was endemic to the rivers of Malabon (Metro
Manila) but has also been collected from the sea at Culion Island
(Philippines). Besides, it is also found thriving well in the brackish
waters and mangrove of Indonesia and Singapore. It is regarded as one
of the smallest fish in the world by mass (av. weight 4.0 to 5.0
mg) and one of the shortest freshwater fish (mature males up to 1.0
cm and females up to 1.5 cm in standard length).
SMALLEST MARINE FISH
o Eviota
zonura [Images] (Naked-headed Goby, Fam. –
Gobiidae):
Widely distributed in the western Pacific, Ashmore Reef (Timor Sea) and Waigeo
(Indonesia) to Samoa, Fiji and throughout Micronesia. Male’s maxmimum length is
1.7 cm and often adjudged to the ‘smallest marine fish’.
Order- Lophiformes
SMALLEST PARASITIC FISH
o Photocorynus
spiniceps [Images] (Anglerfish, Fam. – Linophrynidae):
Widely distributed in the Atlantic and Pacific Oceans. Curiously enough, the
mature males are quite small (6.2–7.3 mm), smaller than any other mature
fish or any vertebrate and remain parasitic on significantly larger
females (up to 5.0 cm).
Order – Siluriformes
SMALLEST CATFISH
o Scoloplax
[Images] (spiny dwarf catfishes, Fam. –
Scoloplacidae), represented by as many as 6 species, is the smallest of
catfishes (max. 2.0 cm) native to freshwater streams and lakes of South
America.
LARGEST / LONGEST / HEAVIEST FISHES:
These fishes are quite diverse representing various Orders of Cartilaginous
to Bony Fishes:
Order – Orectolobiformes
o Rhincodon
typus [Images] (Whale Shark, Fam. –
Rhincodontidae):
Found in all tropical and warm-temperate seas of the world, this is the largest
(12.0 – 18.0 m; 20, 000 kg) pelagic fish, living in open sea (up to about 1,
800 m). This largest fish feeds on smallest ones i.e., filter – feeder.
Order – Lamniformes
o Cetorhinus
maximus [Images] (Basking Shark, Fam. –
Cetorhinidae):
This is supposed to be the second largest (10.0 – 15.0 m; 5, 000 kg)
cosmopolitan migratory species, found in all the world’s temperate oceans,
venturing up to the depth of about 900 m. Like whale shark, it is also a
filter-feeder.
Order – Lampriformes
o Regalecus
glesne [Images] (Oarfish or Ribbonfish, Fam.
– Regalecidae):
It an oceanodromous, world’s longest, ribbon-like, carnivorous bony fish (3.0 –
11.0 m; 270 kg), venturing up to a depth of 1, 000 m.
Order – Cypriniformes
o Catlocarpio
siamensis [Images] (Giant Barb or Siamese giant carp,
Fam. – Cyprinidae):
It is the largest (3.0 m; 300 kg) Cyprinid from the freshwaters of Mae Klong,
Mekong and Chao Phraya river basins of Indochina. Their large size is supposed
to be due to polyploidy (tetraploids). Large-scale cultivation is undertaken in
Vietnam.
o Tor
putitora [Images] (Golden Mahseer, Fam. – Cyprinidae):
On account of habitat loss, habitat degradation and overfishing, this
endangered species has been popular to the fast flowing Himalayan and southern
Asian streams. There was a time when they have been claimed to grow up to 2.5 –
3.0 m (about 54 kg) [but now the catch size is tremendously decreased e.g.,
13.5 cm (28.0 g) – 52.5 cm (1.65 kg) in the streams of Garhwal region (Central
Himalaya).
o Ptychocheilus
luclus [Images] (Colorado pikedminnow, Fam.
Cyprinidae):
It is the largest (1.8 m; 45.0 kg) predatory Cyprinid from Colorado
River basin of North America and one of the largest in the world. Now a days,
the specimens longer than 80.0 cm are an unusual sight.
Order – Acipensariformes
o Huso
huso [Images] (White Sturgeon or Beluga,
Fam. – Acipenseridae):
This anadromous fish from the Caspian and Black Sea basins up to Amur
river in E. Asia, valuable for its ‘roe’ (beluga caviar), is
among the largest (7.2 m; 1, 571 kg) freshwater fish in the world. Today, the
most common catch size is 1.4 – 3.2 m (19.0 – 264 kg).
Order – Osteoglossiformes
o Arapaima
gigas [Images] (Pirarucu, Fam. – Osteoglossidae):
This air breathing longest fish (2.0 – 4.5 m; 200 kg) is the native of
freshwaters of South America (Amazon River).
Order – Tetraodontiformes
o Mola
mola [Images] (Ocean Sunfish, Fam. – Molidae):
Native to tropical and temperate seas of the world, this is supposed to the heaviest
and highly fecund (3.0 million eggs) bony fish (247 – 1,000 kg)
in world. Its average length is 1.8 m and dorsal to anal fin-to fin length
(height) is about 2.5 m (max. 3.3 m; 4.2 m across the fins, weighing up to 2,
300 kg).
Order – Siluriformes
CATFISHES
Some of the world’s largest
freshwater fishes are catfishes, including the predatory European wels (Siluris
glanis, Siluridae; 5.0 m; 330 kg) from central, southern and eastern
Europe; the herbivorous, Critically Endangered, Mekong Giant Catfish (Pangasianodon
gigas, Pangasiidae; 3.0 m; 300 kg) from Mekong basin in Southeast
Asia (Vietnam) and adjacent China and the long-whiskered Piraiba (Brachyplatystoma
filamentosum, Pimelodidae) of South America (3.6 m; 150 kg). The
largest catfishes belonging to Family Ictaluridae in North America are
the Flathead (Pylodictis olivaris, 1.5 m; 56 kg) and Blue
catfihes (Ictalurus furcatus, 1.6 m; 68 kg).
BODY FORM
From typical spindle-shaped
to snake-like (Eels), dorso-ventrally flattened, laterally compressed or
globular external appearance there is also a great anatomical and physiological
diversity. Some species are brilliantly coloured while others are drab. Over 50
Teleosts (mostly Cyprinids, Balitorids, Siluriforms, Amblyopsids, Bythitids and
Gobiids) lack eyes and live in caves. When on one hand there is an exoskeleton
of scales, with adaptive modifications, some species are smooth-skinned
(without scales). A great diversity exists in the locomotory fins, ranging from
absence of any of them to modifications as holdfast organs, lures for
attracting prey, copulatory structures etc. Respiratory diversity ranges from
well-defined typical gills to accessory structures like air bladders or even
lungs like structures. Endoskeleton may be cartilaginous or bony.
BEHAVIOURAL DIVERSITY:
As per the instinct, the wide variety of fishes having chosen to live
exclusively in water, during the course of evolution, had to acquire various
behavioural patterns, obviously, just to minimize the competition of any kind.
Therefore, some exhibit schooling, others are highly territorial; some
practice parental care, others not; some undertaking long or short range
migrations for breeding or feeding purposes (may be anadromous, catadromous or
diadromous, oceanodromous, potamodromous); some showing homing tendencies; some
highly specialised with stinging apparatus, electric organs, sound
production, light producing organs; some indulging in symbiotic (chiefly
commensal) relationships and others showing social behaviour etc. A few species
have been found to be parasitic on other species or on the female of their own
(e.g., Anglerfish, Photocorynus spiniceps ). A wide variety of habitats
compelled them to adapt to a wide variety of foods ranging from microscopic
phyto-or zooplanktons to macro-animals or plants.
An individual species may
tolerate a wide range of temperatures (eurythermal) or a narrow range (stenothermal).
Similarly, they may tolerate a wide range of salinity (euryhaline)
or only a narrow range (stenohaline).
Most fishes are gonochoristic
(fixed sexual pattern) but many are hermaphroditic, either protogynous (vs.
protandrous) sequential (vs. synchronous) hermaphrodites or
where females change to males. Some fishes have a larval stage and undergo
metamorphosis. In general, masses exhibit external fertilization but some
others have adopted strategy of internal fertilization through characteristic intromittant
organs (claspers, gonopodium, priapium, ovipositor etc.)
Lifespan in fishes may vary from
a little over 1 year to about 120 years. Semelparity and iteroparity
are the terms associated with span of life. Semelparous are those (less
than 1 %) which die soon after a single spawning period e.g.,
Petromyzontiforms, Anguillids, Pimephale sp. (a cyprinid), some Osmerids, some
Galaxioids, five species of Pacific salmon (Oncorhynchus) etc. Contrary to
this, majority of species reproduce for more than one spawning season, a
phenomenon called as iteroparity.
FOR THE BENEFIT OF THE STUDENTS
A PRESENTATION HEREAFTER INCLUDES ALL THE ABOVE MENTIONED ASPECTS ALONG WITH
OTHER ASPECTS TO BE DETAILED IN DUE COURSE OF UPDATING
- (Slide No. 1- 14) FISH AND FISH DIVERSITY
- (Slide No. 15) TAXONOMIC CHARACTERS
- (Slide No. 16) TECHNIQUES IN FISH IDENTIFICATION
- (Slide No. 17) FISH COLLECTIONS
- (Slide No. 18) FISHERIES
- (Slide No. 20) AQUACULTURE
- (Slide No. 21) CULTIVABLE FISH
- (Slide No. 22) FISH CULTURE SYSTEMS IN ASIA
- (Slide No. 23 – 24) INDIAN MAJOR CARPS
- (Slide No. 25 – 28) CHINESE CARPS
- (Slide No. 29) ORNAMENTAL CARP
- (Slide No. 30) SUSTAINABLE FISHERIES
