So I asked leading shark ethologist and behaviourist, Professor Samuel 'doc' Gruber to elaborate. After pointing out how much pain women feel when they give birth, making the point that suffering has no effect on reproduction, he reminded me that sharks evolved their mating behaviours and the physical structures involved, separately from other animals.
In a study published recently, scientists from UH Mānoa and the University of Tokyo revealed that two species of deep-sea sharks, sixgill and prickly sharks, are positively buoyant – they have to work harder to swim downward than up, and they can glide uphill for minutes at a time without using their tails.
The survey began in 1986 and is conducted every two to three years. It covers coastal waters from Florida, where coastal shark species concentrate during the winter and spring, north to Delaware, where many shark species migrate during spring and summer as more northerly waters warm. Following this migratory route, at this time of year, makes it easier to survey the whole population.
During their field work this summer NOAA scientists tagged 2,835 sharks, compared to the 1,831 tagged in the previous survey done in 2012.
Every summer, hundreds of whale sharks gather off the Yucatan Coast near the Mexican tourist hubs of Cancun, Isla Mujeres and Isla Holbox. The sharks congregate 32 km offshore to gorge on the eggs of a fish called the little tunny, skimming them from the ocean’s surface with enormous, gaping mouths. In recent years, the spectacle has attracted legions of tourists to snorkel alongside the graceful, slow-moving giants.
Near sanctuary zones at Mangrove Bay and Coral Bay, marine biologists tagged 83 reef sharks. They then tracked the sharks' movements in order to find out how much protection the marine park provides the sharks. Over a two-year period, the movements of blacktip reef sharks, grey reef sharks and sicklefin lemon sharks at Ningaloo Reef were examined.
Yet, since 1987, Discovery Channel, owned by Discovery Communications, has presented 'Shark Week' each summer, deliberately using these important marine animals to create a horror show. Through special effects that dramatically present charging sharks, blood, and teeth, Shark Week falsely presents these varied and often very beautiful animals, as man-eating monsters.
To track the sharks over a long period of time, researchers fitted 20 males and 4 females with satellite tags. These tags sent information about an individual’s position when it came to the water surface.
The smalltooth sawfish is the first documented examples of viable parthenogens living in a normally sexually reproducing wild vertebrate.
The researchers analysed telltale markers called microsatellites in 190 sawfish that reveal how related their parents are. In seven fish, the markers suggested their parents were identical to them. The analysis revealed that the seven fish came from three different mothers.
The shark travelled from the chilly waters off Nova Scotia to the warm, inviting ocean near Venezuela to the clear waters of Puerto Rico and then north again to the waters where he was first caught.
NSU’s Guy Harvey Research Institute (GHRI) began tagging mako sharks in 2009 to study their migratory patterns and now undertakes expeditions worldwide to study them. The school’s marine experts have tagged mako sharks as far away as Mexico and New Zealand. In addition to makos, they have also tracked tiger, oceanic white tip and sand tiger sharks, as well as blue marlin.
According to study leader Dr Yuuki Watanabe of the National Institute of Polar Research, Japan, "The physiological mechanism of keeping heat in the body is well understood. But, more a fundamental question is, why this unique evolution occurred in the first place. In other words, what kind of advantages does the fish gain from being warm-bodied?"
Researching the intelligence of the grey bamboo shark a team of researchers at Rheinische Friedrich-Wilhelms-University in Bonn, Germany showed that sharks could be trained to recognise and remember shapes for an extended period of time.
First juvenile sharks were subjected to three different cognition experiments, one at a time, and then tested to see how long the sharks could remember their training.
