Pelagic fish reproduction

Fuse shut

Reef fishes have developed a diversity of reproductive strategies to maximize survival of their offspring.

They have an enormous fecundity compared to higher vertebrates.
Depending on the species, they can spawn clutches of eggs daily, weekly or monthly or a few times a year. Spawning is secretive and typically only occurs during very specific and brief periods throughout the day.

The majority of reef fishes spawn into the water column (pelagic eggs) or on the bottom (demersal eggs).

Pelagic spawners shed their eggs directly into the water column after rising off the bottom. Such eggs are usually small, transparent and spherical and always slightly buoyant which allows them to be dispersed by currents.

Pelagic spawning is the most taxonomically widespread spawning strategy among reef fishes. It is characteristic of thirty-six reef fish families, including popular aquarium fish groups such as the tangs and surgeonfishes, butterflyfishes, wrasses, hawkfishes, and all marine angelfishes.

Demersal spawners, by contrast, lay their eggs in a pre-selected area on the bottom and care for them until they hatch. The area and nature of the nest depends on the species. The majority, like the damselfishes, blennies gobies attach their nest onto a substrate.

A pair of demersal spawners (Fiji blue devil damsels). As female deposits her eggs the male fertilizes them.

A few groups lay eggs balls (e.g. dottybacks), others build nests to hold their eggs (e.g. fairy basslets), and some even brood their eggs orally (e.g. most cardinal fishes) or in a pouch (e.g. seahorses). In all cases the male incubates and defends the eggs until they hatch. A few reef fishes, like the rabbitfishes, are egg scatterers and spawn sinking (demersal) eggs that are randomly scattered across the bottom.

Fecundity and the survival of reef fish offspring are usually inversely related. Generally, pelagic spawners place their reproductive effort into spawning frequency and/or egg numbers, producing large numbers of eggs with a spawning season.

For example, the pygmy angelfishes spawn every evening each time producing up to 2, 000 eggs. Groupers spawn less frequently but when they do they produce millions of eggs.

Pelagic eggs are tiny (less than 1 mm for most pelagic spawning species) and soon after being fertilized (usually within 24 hours). At hatching the larvae are small and poorly developed and therefore have a slim chance of survival. Pelagic spawners therefore reproduce at times when environmental conditions maximize survival of the offspring.


Seasonal migrations of blue whiting in the Norwegian Sea in 1978 to 1982 (C.M)
Book (International Council for the Exploration of the Sea, Pelagic Fish Committee)

Actually your notions about frozen fish may be

2008-07-14 15:57:30 by part_of_the_problem

While *truly* fresh fish is superior to frozen for texture in many cases, what passes as "fresh" is often not really that fresh.
If you ever had the kinds of pelagic fish you describe within 30-60 minutes of being caught, you would be amazed at how un-fishy they are, especially tuna.
When fish is fileted and flash frozen at sea in that same time frame, it will most likely have less of a fishy flavor than the same fish that stays unfrozen for even a few hours trip to market, which is enough time to develop a fishy enough taste to put off someone who is sensitive to it.


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