Researchers at Woods Hole Oceanographic Institution (WHOI) unveiled a hazardous cocktail of pesticides when analysing the brain matter of 12 marine mammals; eleven cetaceans and one gray seal stranded near Cape Cod, Massachusetts.

This is the most extensive study of pollutants in marine mammals’ brains and it confirms suspicions of marine mammals being the carrier of a vast array of different chemicals that have found their way into marine ecosystems.

Lead author Eric Montie analyzed the cerebrospinal fluid and the gray matter of the cerebellum in the twelve animals and found them to contain a long row of different man-made chemicals, including a group of especially widespread substances labelled “the dirty dozen” by environmentalists. Many countries banned the “the dirty dozen” as early as the 1970s due to their adverse effect on human health, but they are unfortunately still present in our environment.

Montie didn’t just test for the presence of certain chemicals; he also measured their concentration and found one instance where it was surprisingly high.

“The biggest wakeup was that we found parts per million concentrations of hydroxylated PCBs in the cerebrospinal fluid of a gray seal”, says Montie. “That is so worrisome for me. You rarely find parts per million levels of anything in the brain.”

PCBs are neurotoxicants known to disrupt the thyroid hormone system. Other examples chemicals found in the tested mammals are DDT (diklorodifenyltriklorethane), which can cause cancer and disturb reproduction, and PBDEs (polybrominated diphenyl ethers); a type of flame retardants known to impair the development of motor activity and cognition.

Co-author Chris Reddy, a senior scientist in the WHOI Marine Chemistry and Geochemistry Department, describes the new study as “groundbreaking because Eric measures a variety of different chemicals in animal tissues that had not been previously explored. It gives us greater insight into how these chemicals may behave in marine mammals.”

The results of this study was published online April 17 in Environmental Pollution.

Commercial, recreational and party/charter boat fishermen from Maine to North Carolina have all rallied together to deal with an out-of-balance population of predatory spiny dogfish sharks that threatens the recovery of New England groundfish and several others fish stocks living along the U.S. East Coast.

The newly formed Fishermen Organized for Rational Dogfish Management (FORDM) has requested the assistance of Dr. Jane Lubchenco, newly appointed National Oceanic and Atmospheric Administration head, in dealing with the predator.

Spiny dogfish

The disproportionate abundance of dogfish is not a new problem; as early as 1992 Dr. Steven Murawski, now chief scientist of the National Marine Fisheries Service’s, wrote “Given the current high abundance of skates and dogfish, it may not be possible to increase gadoid (cod and haddock) and flounder abundance without ‘extracting’ some of the current standing stock.”

That was over 15 years ago and the situation has not improved. On the contrary, the amount of dogfish now exceeds that of skates, and dogfish comprises over half of all fish taken in the annual trawl surveys carried out by the Northeast Fisheries Science Center.

The spiny dogfish can exceed 150 cm in length and preys on virtually all species of fish smaller than itself. Dogfishes can also create a problem for other species by competing with them for prey fish.

This remarkable abundance of dogfish is most likely the result of countless years of ever increasing over-fishing. Spiny dogfish is not an appreciated food fish and the depletion of other species seems to have favoured it greatly in these waters.

This story might be a few days old but is still of interest and as I haven’t been able to get to it sooner I decided to post about it today.

Indonesia will allow trawling in selected areas for the first time in 30 years, maritime ministry official Bambang Sutejo announced on January 15. Trawling will be allowed off four areas of Indonesia East Kalimantan province, despite concerns about overfishing.

“There will not be overfishing this time as we’re only allowing small boats to trawl, and it’s not allowed in other parts of Indonesia,” says Sutejo, adding that legalising trawling would help fight illegal trawlers.

According to Chalid Muhammad of the independent Green Institute, trawling has a destructive impact on the marine environment and will intensify the problem with overfishing in Indonesian waters. “The total amount of fish caught is getting smaller each day while their imports are getting bigger,” says Muhammad.

Muhammad also feels a legalization of trawling will embarrass Indonesia as it prepares to host the World Ocean Conference. “If the government allows this, Indonesia will have a weak standing during the World Ocean Conference as sustainable management of marine resources will be discussed,” Muhammad said. The World Ocean Conference is an international gathering of policymakers and scientists held in May 2009.

Kalimantan is the Indonesian portion of the island Borneo, the third largest island in the world, and is divided into four provinces: East Kalimantan, West Kalimantan, South Kalimantan, and Central Kalimantan.

What is trawling?

Trawling is a fishing practise where fishing boats tow long nets behind them. These nets do not only scoop up commercially valuable fish, but all sorts of marine life. Trawling is divided into bottom trawling and midwater trawling, depending on where in the water column the trawling takes place. Bottom trawling is especially harmful to marine environments since it can cause severe incidental damage to the sea bottoms and deep water coral reefs.

A research group[1] studying the hunting ability of the great white shark has found evidence indicating that this notorious predator actually has a fairly weak bite. In several movies – including the legendary Spielberg film “Jaws” – the great white shark has been portrayed as a hunter blessed with an exceptionally strong bite, but the allegedly fierce jaw power of Carcharodon carcharias is now being questioned.

According to research leader Dr Daniel Huber of the University of Tampa in Florida, sharks actually have very weak jaws for their size and can bite through their prey mainly thanks to their extremely sharp teeth – and because they can grow to be so large.

Photo by Terry Goss, copyright 2006

“Pound for pound, sharks don’t bite all that hard,” says Dr Huber. Compared to mammals, sharks have amazingly weak bites for their size. Lions and tigers are for instance equipped with much more jaw strength than sharks when you account for body size. According to Huber, mammals have evolved much more efficient jaw muscles.

During the study, Dr Huber and his team studied 10 different shark species. The bites of small sharks were fairly easy to measure, while large sharks had to be knocked out and subjected to mild electricity in order to stimulate their jaw muscles.

As mentioned above, sharks don’t really need strong jaws since they can grow so large and are fitted with extraordinarily sharp teeth. In addition to this, they also benefit from having very wide jaws. When they tear an animal apart, they frequently use a sawing motion.

Dr Huber hopes that their study will lead to the development of protective swim wear and other types of shark-proofing gear.

If you wish to read more, you can find the study “Is Extreme Bite Performance Associated with Extreme Morphologies in Sharks?” in the journal Physiological and Biochemical Zoology.

http://www.journals.uchicago.edu/doi/abs/10.1086/588177?prevSearch=(shark)+AND+[journal%3A+pbz]