Indian Ocean Dolphin Population Plummets Due to Commercial Fishing
The fishing operations that have had dolphins swept up as bycatch have meant that nearly 4 million dolphins have died since 1950 and the population of dolphins in the Indian Ocean has declined by nearly 80 percent, as The Guardian reported.
Those numbers just represent the dolphins killed directly as bycatch of drifting nets that trail behind large fishing boats and do not represent the number of dolphins, porpoises or whales killed by floating ghost nets, harpoons, other types of tuna fishing or animals that are injured and succumb to their wounds later. That means the actual number of dolphins killed from commercial fishing may actually be much higher, according to the study.
Looking at driftnets, which account for just over one-third of Indian Ocean commercial fisheries, the researchers were able to calculate that the number of dolphins, porpoises, and whales killed directly each year as bycatch peaked at around 100,000 from 2004 to 2006. That number has come down slightly and is now around 85,000 cetaceans annually, according to the study.
Unfortunately, the authors do not believe the decline in bycatch is the result of improved practices, which are essentially unregulated. Instead, they believe it reflects the declining dolphin population, according to The Guardian.
The study's lead author, Charles Anderson of the Manta Marine organization in the Maldives, estimated that the dolphin numbers had probably dropped to only 13 percent their pre-1980 levels, which is when large-scale tuna fishing in the Indian Ocean began, as The Guardian reported.
"Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable," the study says. "Indeed, mean small cetacean abundance may currently be 13 percent of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue."
There are many limitations in obtaining the exact number of mammal deaths due to bycatch, one of the study's author's told The Guardian, especially considering that most dolphins caught up in driftnets were not registered and were likely tossed over the side of the boat. These types of nets also snare turtles, whales and sharks.
The researcher, Puti Liza Mustika, from James Cook University's College of Business, Law and Governance, clarified that most of the bycatch was dolphins and that there was some reliable data from observers on boats and from previous studies. However, as a researcher, some clearer numbers would be helpful.
"That bycatch number is alarming, but there are a lot of uncertainties because the datasets are insufficient," Mustika told The Guardian.
Adding to an element of uncertainty is that Iran and Indonesia, the countries that run the two largest tuna operations in the Indian Ocean, have no system of reporting cetacean bycatch. Consequently, Iran's average annual bycatch of 214,262 tons of tuna likely kills more than 30,000 dolphins, porpoises and whales every year, according to the study, as The Guardian reported.
"It's a painful death. Dolphins are clever, but because the net is very thin in the water, the dolphins' sonar misses them," said Mustika to The Guardian. She added that the impetus to solve the problem is on scientists and tech companies. "The solution has to be technology, as well as using fishing gears that are more sustainable. But banning these fishers is not a solution for developing countries."The study concluded that oversight is needed, saying its findings showed "the need for much improved monitoring, mitigation and management."
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
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