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.
A simple fish stock assessment model applied to over 500 years of catch data demonstrated that if Canadian authorities had allowed for the rebuilding of the stock of northern Atlantic cod off Newfoundland and Labrador in the 1980s, annual catches of about 200,000 tonnes could have been sustained.
Traditional fishing pirogue in Madagascar. Photo by Jonathan Talbot, World Resources Institute, Flickr
Substantial growth in the number of motorized vessels operating in the Mozambique Channel region between East Africa and Madagascar in the past 65 years has led to a 60-fold increase in effective small-scale fishing effort and a 91 per cent decline in Catch Per Unit of Effort (CPUE).
Warming waters from climate change are modifying freshwater fish communities everywhere, notably in Lake Peipsi, located between Estonia and Russia, as they favor warm-water species such as pike-perch and hinder the survival of cool-water species such as vendace and burbot. Continue reading
Recreational fisher at Baker Beach, California. Photo by mgstanton, Flickr.