Carp Seed Procurement & Reproductive Biology

Carp Seed Procurement

• Quality seed availability in adequate quantities forms the basis for sustainable aquaculture.
• Naturally, Indian major carps and Chinese carps exclusively breed in flowing waters during the rainy season.
• Prior to induced breeding, natural waters were the source of required seed, but they were commonly contaminated.
• Artificial breeding techniques and hatcheries help meet demands from fish farmers.
• Induced breeding allows consistency and spawning on demand and provides opportunity for stock improvement through selective breeding.

Reproductive Biology

• Teleosts primarily use sexual reproduction, though parthenogenesis occurs rarely as seen in the Amazon molly (Poecilia formosa).

Number of Breeding Opportunities

• Synchronous fish reproduce annually or once in their lifetime, with all oocytes developing simultaneously. Salmonids are an example, where the fish dies after spawning.
• Group synchronous fish possess two or more oocyte populations, ovulating once per season or undergoing multiple ovulations within a spawning season, as evidenced by most fish species.
• Asynchronous fish, such as zebrafish, ovulate regularly, even daily, over extended periods.

Size and Age at First Maturation

• Maturity age varies among species based on geographical and ecological factors.
• Common carp matures at one year, rohu and mrigal at 1+ years, while gross carp, silver carp, and catla mature at 2+ years.
• Even within the same region, maturity age differs based on ecological conditions and intrinsic factors.
• Induced breed species in pond culture mature earlier than riverine stocks.
• Cultivable carp males generally mature sooner than females.

Time of Spawning, Duration, and Season of Reproduction

• Cultivable carps like Catla, Rohu, mrigal, silver carp, and grass carp breed during the monsoon (July-August) in most of India.
• The spawning season depends on monsoon onset, varying regionally; carp breeding occurs earlier in Assam than in Orissa or Bengal.
• Spawning common carp is easier than other carp species.
• Common carp has two breeding seasons: monsoon and post-winter (February-March).
• Indian and Chinese major carps naturally breed in flooded rivers during monsoon season. It is the suitable time for induced breeding.
• CARPS (IMC) breed from April to September during the monsoon.
• Common carp breeds from February to March and again from August to September.
• Grass and Silver carp breed from April to September during the monsoon season.
• Catfish spawns during monsoon periods.

Type of Spawning

Open Substrate Spawners

• A pelagic spawner is a species that sheds pelagic eggs into the water column.
• The eggs, embryos, and larvae of pelagic spawners have high water content, or contain oil globules.
• Tuna and sardines are examples of pelagic fish.
• Some demersal fish, for example, coral reef fish like parrotfish, leave the bottom to spawn pelagically.
• Benthic spawners are spawners deposit their spawn on or near the bottom, for example, cod and flatfish.

Egg Hiders

• These fishes conceal their eggs without providing post-hiding care.
• They are usually benthic spawners burying fertilized eggs, such as salmon and trout that dig nests (redds) into the gravel using their tail
• Females deposit and males fertilize the eggs, both defending the redd.
• After both fish bury and abandon the nest site
• Annual killifish, known to bury eggs, deposit their eggs in mud; parents die as waters dry, and eggs hatch as rains stimulate them.

Bearers

• These are fishes that carry their embryos either externally or internally.

External bearers

• These are mouth brooders that carry eggs or larvae in their mouth
• Mouth brooders can be either ovophiles or larvophiles.
• Ovophile or egg-loving mouth-brooders lay eggs in pits for females to suck up in the mouth, where hatching and fry development occur.
• External fertilization can happen, where the male uses spots on the anal fin that contain colour to attract females, who try to pick the spots up and instead fertilize the eggs
• Many cichlids and more labyrinth fish are ovophile mouthbrooders.
• Larvophile or larvae-loving mouth brooders deposit eggs on substrate, and the female picks the eggs and guards them till they hatch, picks up and keeps them in her mouth after they hatch and releases them only when the hatchlings can fend for themselves
• Some eartheaters are larvophile mouthbrooders.

Internal bearers

• The beginning for live bearing happens with facultative, or optional, internal pregnancy, where species of killifish lay eggs but also accidentally fertilize females that retain them.
• These eggs release usually without a lot of time for embryonic growth
• The next part of live bearing evolution involves a process where the female carries all embryos, with the only source of nutrition being the egg yolk itself
• Marine rock fishes and also Lake Baikal sculpins have this situation, named ovoviviparity
• This strategy allows them to reproduce in larger numbers the same as pelagic fish, while also protecting the young through their vulnerable stage
• By contras sharks and rays utilizing this strategy manufacture a smaller number of eggs, with shorter spans associated to species that place embryos in environment surrounded by horny shell, and longer periods associated to retaining fish, and developing swimming ability
• Fish can be classified into Lithophils, Phytophils, Psammophils, Ostracophils or Pelagophils

Mating System

• Promiscuous systems involve multiple sexual partners for each sex during breeding, as seen in herrings and cod.
• In fishes, this is the number one or most common, where mates make no choice but breed multiple times in parallel or at the same time
• Polygamous mating is when one has multiple mates as the opposite sex only has one another (sunfish, tilapia, catfish), with the evolutionary goal of passing along important traits
• Polygamy can be expressed as polygyny, where one male mates with many male, or polyandry, where one feme mates with many males

Gender System

• Gonochoristic biology describes the property of having only one distinctive trait being one organism
• It's seen in fish often
• Hermaphroditic mature fish possesses male/ testes and female ovary ex glands at the same time
• It can produce cross fertizilation as spanning is in progress, with the Serranidae that are females first or are evenly developed
• Sex can shift after growth through maturation (Sea beam)

Spawing site Prep

• Can spawn with no prep, or from broadcast
• Can prepare spawning area that is deended, Tilapia and salmon

Location of Fertilization

• Ecternal fertilization exists for aquatic life, where the eggs/sperm are added into the body of water and takes place

Oviparity

• Ovliparity implies the female casts unleaded eggs so that external fertilization creates offspring (eels etc) through both genders shedding gamete in the medium

Ovoviviparity

• Eggs grow within a mother after internal sex until they have a food supply which the Yolk gives in a individualistic cycle

Viviparity

• Similar situations to ovoviv parity through the embryos have the ability to extract direct nourishment like mammals, or are advanced beyond birth

Types of fish eggs

• Pelagic Eggs: Most species eggs are small, between 0.7 MM and 1.5 MM in diameter with spherical, transparent anchovies, smaller than demersal with no sticky membrane with a single oil glob, they float
• Demersal eggs: sink and the are laid in 2 types with an adhesive membrane or in mass