AKU3201 PRINCIPLES OF AQUACULTURE Natural spawning Induced spawning

Problem Availability of required quantity of fish seed Seed from wild Low seed supply

Broodstock –> larvae -> fry -> fingerling -> juvenile

Spawning habits differ considerably in different groups of fish Season-bound spawners and spawn in particular seasons such as spring, summer, rainy season and winter Non-season-bound ones and spawn round the year

Spawning conditions: i) spawn in confined waters, ii) others in fluviatile conditions; iii) some migrate from freshwater to the sea or from the sea to freshwater to spawn.

Natural spawning Induced spawning

Natural spawning Stimulation of natural spawning conditions in ponds or tanks Seasonal – spawn at certain season (rainy, flood, spring) Non-seasonal – spawn throughout the year

Tilapia species - Nest builders; fertilized eggs are guarded by brood parent Sarotherodon species - Mouth brooders - Either male or both male/female Oreochromis species Mouth brooders Female only

Genital papilla Nile Tilapia Nile Tilapia = male establishes a territory & a round nest, female enter & lay eggs, male fertilized the eggs, female collects & incubate eggs in mouth, eggs yellow in colour, egss hatch in five to seven days, fry remain another 4-7 days. Male: 2 openings Female: 3 openings

300 gm female broodstock: 250-300 eggs Eggs fertilized by male Female collects & incubate eggs in mouth Eggs yellow in colour Hatch about 5-7 days

Identify male & female 1 male : 3 female into hapa

Induced spawning Species that didn’t reproduce in captivity Obtain fish supply outside of the normal spawning season; important for intensive culture Develop superior strains through selective breeding & hybridization methods Maximize survival; 1% natural spawning; 65% induced spawning

Induced spawning Environmental manipulation Temperature Water volume pH Salinity Hormone induction

Primary tissue involved in hormonal cascade Hypothalamus Pituitary gland Gonad

Broodstock (Induk) Large Productive Healthy Disease-free

Hypophysation: Process of inducing fish to spawn through the use of hormones E.g., Pituitary gland & other hormones

Commercial hormone HCG – Human chorionic gonadotropin LHRH – Luteinizing hormone-releasing hormone GnRH –Gonadrotropin-releasing hormone FSH – Follicle-stimulating hormone Ovaprim, ovaplant, ovatide

Pituitary gland

Steps in artificial propagation Brood fish selection from nature or fish ponds Brood fish rearing Induce final maturation & ovulation with hormone treatment Treatment of the male & milt collection Stripping of the female & egg collection Artificial fertilization Incubation & hatching of eggs Larvae & fry rearing

(1) Broodstock selection (2) Hormone preparation & injection (3) Stripping of eggs & sperm (4) Fertilization & incubation (5) Hatching & larvae

Sex Identification External - Shape of body (abdomen) Colour (Male => colourful) structure (Male => tubercles on operculum surface) Eggs/ milt

Weight & inject Male - 0.25 ml/kg Female – 0.5 ml/kg Leave ~ 8- 10 hours, temperature 26-28oC

Internal Check for egg & milt through catheter Gonad (dissection, histology)

Identify the sexes Male genital papillae – pointed Female gential papilale – oval shape, bulging abdomen

INJECTION THE FISH 2 dosage level Intraperitoneal – within the body cavity, behind either pelvic or pectoral fin 2 dosage level A prepatory dose – brink of spawning A final dose – induces ovulation A time gap generally 12 to 24 hour between the dose

Stripping

Eggs

Male spawner Some fish – difficult to strip Due to the anatomical structure – seminal vesicles Need to sacrifice the fish to collect the milt Avoid contact with water or the spermatozoa lose its ability to fertilize mature fish eggs. Milt can be stored in a refrigerator for 1-2 days

Collection of milt from catfish testis

Spread on a screen (mesh size 1 mm), hatchling will pass the screen & dead eggs & shells remain on the screen