Common seadragon. Photo by Melanie Warren.
Despite their odd shape, which makes them resemble a tuft of seaweed, common and leafy seadragons grow in the same fashion as other bony fish, new research has found.
Atlantic cod (Gadus morhua) is among the fish species maturing and spawning earlier in the “spring” reproductive season, due to higher water temperature. Photo by GRID-Arendal, Flickr.
Fisheries managers and researchers may now predict how early fish will spawn in response to warming waters due to climate change, both in the oceans and in freshwaters.
Mandarin fish mating. Image by Klaus Stiefel, Flickr.
Discounting anthropogenic-induced changes, the seasonally oscillating environments where long-lived fish hatch and grow remain more or less the same throughout the course of their lives. This means that the common explanation that states that fish become sexually active – or spawn for the first time – after experiencing certain environmental stimuli does not properly explain this phenomenon.
For more than 40 years, Dr Daniel Pauly, principal investigator of the Sea Around Us initiative at the University of British Columbia’s Institute for the Oceans and Fisheries, has been collecting evidence to further develop his Gill-Oxygen Limitation Theory, also known as GOLT.
Back in 2010, he presented his findings in a slim book titled Gasping Fish and Panting Squids: Oxygen Temperature and the Growth of Water Breathing Animals, whose second edition has just been released; a Chinese edition will soon follow.
A pair of One-spot Pullers (Chromis hypsilepis) preparing to spawn. Home Bommie, Ulladulla, NSW. Photo by Richard Ling, Flickr, CC BY-NC-ND 2.0.
In over 80 per cent of fish species, the females, including those known as ‘big old fecund females,’ or BOFFS, grow bigger than the males. This long-established fact is difficult to explain with the conventional view of fish spawning being a drain on the ‘energy’ available for growth. If this view were correct, females, which are defined by their larger reproductive effort, would always remain smaller than males.