We have long heard about a shark's acute sense of smell. It's ability to detect the odors or scents given off by an injured fish was long considered one of a shark's primary tools in its predator tool kit. But just how sensitive is it? With currents or water motion moving odors around, just how does a shark sense a smell and then begin tracking it to its source? Dr. Jelle Atema has been studying sharks for some 20 years, working with the Boston University and the Woods Hole Oceanographic Institution. He has spent considerable time investigating just how sharks utilize their sense of smell to their best advantage. Reporting in BU Today, Susan Seligson writes of Dr. Atema's work with smooth dogfish, a small shark that is often found in the U.S. northeast (BTW: And one that has been severely hit by commercial shark fishing operations). Using controlled plumes of odors like squid scent in a long observation tank, he is unlocking many of the secret subtleties as to how a shark senses odor and tracks it to its source. Often we think of sharks as sensing the smell given off by an injured animal. That may be true but, when hunting, sharks are attracted to the odors of familiar prey, injured or otherwise. “All animals give off some kind of body odor,” says Atema.“The science here is to understand how odor is dispersed into the water, and how many molecules does a shark need in his nose to track that odor.” Dr. Atema's experiments have also provided new insight as to how a shark responds to odors and how they just where to go to get to the source. As reported in BU Today, "Working along with Jayne Gardiner at the University of South Florida, in Tampa, Atema’s most recent discovery is that sharks are guided by the nostril that first detects the prey’s odor, rather than orienting themselves based on which nostril senses the greater odor concentration. The finding—that smell reaches one nostril before the other, signaling whether to veer left or right—means that sharks can decipher very quickly, a matter of seconds as opposed to minutes, where their next meal is, no matter how chaotic the dispersed odor plume. Before this discovery, published in Current Biology, scientists had long believed that sharks’ sense of smell was a function of the plume’s surface area—the bigger the plume, the easier it would be for sharks to smell it." In some respects, the ocean is a very smelly place, full of scents or odors of hundreds of different organisms and at varying strengths or intensities. Bombarded with all these stimuli, sharks can amazingly sort it all out and, along with its other senses, be the efficient predator that it is. Source: RTSea
Norwegian scientists studying marine life in the Pacific Ocean have successfully tested a robotic shark spotter. The robot resembles a lemon-coloured surfing board. It detects a shark at a distance of up to 300 metres and reports its discovery to researchers via a satellite.The device has already been used for spotting great whites. Tags: 
A great white shark seems to keep its distance from its fellow white sharks. Even when I have had the opportunity to have as many as five white sharks circling around me, they still keep a respectable distance from each other and rarely came close to each other. Then on the other hand, you have hammerhead sharks that can be seen swimming in large schools. Lemon sharks or various types of reef sharks congregating in the tens and sometimes hundreds. And I have seen seasonal congregations of up to 4-5 foot leopard sharks and guitarfish in Southern California, presumably part of a breeding behavior. The social interactions of sharks is not well understood. Each species has its own type of behavior and while the general public thinks of sharks as somewhat solitary (which they often can be), in reality it is more likely a very complex relationship that revolves around feeding, breeding, and a predator's sense of territoriality (ie: survival). In Australia, one researcher is specifically focusing his efforts on understanding the social behavior of sharks. Working in conjunction with the 