However, as the jumbo squid’s “switch” from one to two year life cycles depends on ambient water temperature, another strong El Niño event may cause almost complete disappearance of the large group, returning the populations to their “normal condition” as a medium size annual breeder. The total annual catch of 600,000 to 1m tonnes has become extremely important for coastal livelihoods of eastern Pacific countries. In fact, these climate events have triggered the establishment of large bi-annual groups of squid weighing 25-40 kg-ten times their normal size.Īfter the El Niño/La-Niña events of 1997-2000 these squid began to make their way up the Pacific coast to northern California reaching Alaska, leading to the recent development of one of the world’s largest squid fisheries. But during this second year they continue to grow fast meaning that by the end of their two years they attain much larger sizes. The colder waters during a La Niña delay their maturation and allow them to survive into the next year, giving them a two-year life cycle. However, a strong hot season of El Niño followed by a cold season of La Niña can do funny things to these squid. It lives in the warm waters of the eastern Pacific and has supported small-scale fishing in Mexico, Chile and Peru. Also known as the Humboldt squid, it typically weighs around 1-2 kg and has an annual life cycle. The “jumbo squid” represents one of the most striking examples. Extreme climate changes lead to population explosion At a time when life in the oceans is threatened, cephalopods seem able to buck the trend. Bottom-dwelling octopus and cuttlefish who live relatively static lives are thriving, as are squid that hover over the bottom, along with those in the open ocean that may travel thousands of kilometres from spawning to feeding sites. We used data from both regular commercial fisheries and specific research surveys.Įverywhere we looked we found a substantial and statistically significant increase. Most were “target” species deliberately sought by fishermen, others were non-target or bycatch species. We used an extensive dataset of 35 different species (52% squid, 31% octopus and 17% cuttlefish) from all major oceanic regions. To get a better estimate of their overall abundance, we looked at what we call catch rates -how many were caught per vessel per unit of time -over the past six decades. These are elusive creatures, notoriously difficult to count. These traits enable cephalopods to adapt rapidly to changes in the environment which have become even more pronounced in recent decades thanks to human activity. They produce lots of eggs, and their eggs have relatively low mortality rates, whether thanks to patient brooding by an octopus mother or the protective mucous that covers embryonic squid. Squid, octopus and cuttlefish live in the “fast lane”, growing quickly and typically living for only one or two years. The vacant space left by fish may be occupied by other species, with rapidly proliferating animals having a clear advantage. Fishermen fish out the top predators first, including large sharks, tuna and whales, and then medium size fish such as cod, hake and halibut that usually live long and grow slowly. In terms of the food web, we tend to start from the top and fish “ downwards”. Humans have reached and in many cases surpassed sustainable fishing limits, as our growing population demands more food. These fast-growing, adaptable creatures are perfectly equipped to exploit the gaps left by extreme climate changes and overfishing, according to a study colleagues and I published in the journal Current Biology. Squid, octopus and cuttlefish populations are booming across the world.
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