Military Tag 20 Sharks In The Eastern Pacific
Sixteen military personnel representing the Army, Navy and RAF have just returned from an ambitious diving expedition to tag endangered sharks around several remote Pacific islands off the west of coast of Mexico. The expedition travelled from Guadalupe to the Revillagigedo Islands from 19 Oct – 07 Nov 2008.
The expedition, called EXERCISE JURASSIC SHARK 2, was the second shark tagging expedition to be conducted by the Joint Services Shark Tagging Team. The aim was to contribute to shark conservation around Guadalupe and the Revillagigedo Islands in the Eastern Pacific by tagging a total of 20 sharks. The expedition set out to tag great white and scalloped hammerhead sharks in order to gather information on their movements. The tags send signals to underwater radio receivers allowing the movements of the sharks to be recorded.
All tagging was carried out whilst the sharks were free swimming as this is the least stressful method for the animal. The expedition started at Guadalupe, west of the Baja California where 10 great white sharks were tagged from the surface under the direction of a locally-based scientist. Sharks were also observed from a cage from where the team photographed a large female shark never before seen at Guadalupe. The team now have the responsibility of naming this shark on the database of great white sharks found around the island (now 86 individuals).
Four days were spent tagging great whites before the team headed south to the Revillagigedo Islands, a largely uninhabited group of volcanic islands to the south of the Baja California peninsula, where they begun the far from easy task of tagging scalloped hammerheads sharks; an exceptionally skittish species. All diving from here onwards was carried out in open water in areas that should have been prime shark habitats. Tragically, the effects of shark fishing meant that hardly any sharks were seen until the team reached an isolated rock outcrop just 80 metres long called Roca Partida. Four man dive teams dived three times per day on a rotational basis in order to optimise the use of the spear guns used for tagging. Strong currents, huge swell, sheer rock walls, extreme depths and the presence of sea urchins made this a difficult site from which to tag sharks. Nevertheless, 6 hammerhead sharks, 3 Galapagos sharks and a silver-tip shark were eventually tagged. Tissue samples were also taken from 2 manta rays for DNA and toxin analysis.
The research work carried out by the expedition took place in co-operation with two Mexican marine research organisations: The Centro De Investigaciones Biologicas del Noroeste, S.C. (CiB), Mexico and the Centro Interdisciplinario de Ciencias Marinas (CICIMAR). The expedition was sponsored by the Joint Services Expedition Trust and approved by the Royal Geographical Society. The scientific equipment was purchased with funds from Selex Galileo.
The expedition was led by Major Andy Reid (Army), who explained, “An expedition such as this is all about experiencing controlled exposure to risk with the aim of developing the kind of leadership, teamwork, courage and co-operation that is vital to military operational capability. The expedition also assisted with two important conservation projects, both of which exploit the skills of a Joint Services team to best effect. Sharks are in dramatic decline around the world and this is our chance to make a difference by establishing those parts of the shark’s habitat that most need protection.”
Corporal Tim Gort (Army), another member of the expedition said, “The expedition has been hugely ambitious and an incredible experience. The rate that sharks are being needlessly killed is unsustainable and most are now endangered. The work we have done will result in a better understanding of shark movements and help in the development of national and international strategies for their protection.”
Overall, the expedition succeeded in tagging 20 sharks with radio tags and placed 4 radio receivers. Tissue samples were also taken from great whites and manta rays. Capt Richard Beck (Army) tagged a great white and said, “It is not every day that you are able to tag a 5 metre great white shark; this expedition really brought home to you the value and beauty of sharks.”
The team hope to build on the success of Jurassic Shark 2 with another expedition in summer 2010.
Further information can be found on the expedition website at www.jurassic-shark.org.uk
Side-Scan Sonar Review
HUMMINBIRD
797C2 & 1197C SI COMBO
Today, divers are much more likely to use a professionally run hardboat, and complain bitterly if the skipper doesn’t put the shotline into the centre of the wreck. We take it for granted that he knows where it is.
Echo-sounders go a long way to relieving this problem, but they need careful interpretation. The clever technical divers of previous times could find a wreck using a magnetometer, towing a “fish” behind the boat and looking for magnetic anomalies in the seabed. It was never that reliable, and you needed to be dedicated, systematic and have plenty of manpower available to use one efficiently. Today we have the magic of side-scan sonar, which simply puts a picture of what’s down there up on the LCD screen – provided you know what you’re looking at.
Side-scan sonar has until now been applied in the same way as a magnetometer, using a fish to get the transducer away from the turbulence caused by the hull moving through the water. Mounting the transducer on the hull always caused too much “noise”.
But we are undergoing a digital electronic revolution. It’s not just a question of getting the “ping” right. Software writers have learned how to turn the “ping” into information that almost any of us can understand, and it’s the software that makes the difference.
HUMMINBIRD, A DIVISION of the US giant Johnson Outdoors, produces a range of echo-sounders (or “fish-finders”) that give a sort of picture of the seabed. For use in small boats, these can be combined with a GPS chart-plotter. And now you can get an economically priced dual-beam side-imaging sonar that can really tell you whether it’s a wreck or a mound of sand. Its transducer is readily mounted on the transom of the RIB, or can be included as a through-hull unit on larger vessels.
There’s never much space in a RIB, which makes the new compact 797c2 SI Combo a good prospect. Hardly bigger than a typical fish-finder, it sits on a standard Humminbird mount and can be detached quickly when leaving the boat moored overnight. Complete with transom-mounted transducer and everything you need to make it work, it still doesn’t break the sacred £1000 barrier.
One gloriously wet day in September, we set off to sea in a little 6m RIB to see if it was as easy to use as the salesman said. Our boat had been temporarily kitted out with the Humminbird 1197c SI Combo which, besides having four additional buttons for user-selected short cuts to the different functions, works in exactly the same way as the 797c2 SI Combo, but has a screen twice the size.
In fact it was rather big for the boat and occupied most of the space available on the console. It also costs twice as much, but it made photography easier in the appalling conditions.
It also allowed us to have both chart-plotter and sonar functions working simultaneously and still let all three of us see what was going on without crowding the unit and obscuring its view of the GPS satellites, but I will describe the functions assuming it to be the smaller unit. Naturally, the GPS function gives speed over the ground and course. You can look at it as a conventional chart, with a perspective that matches the coxswain’s view, or with a real image from Google Maps laid over it.
This makes interpretation of where you are, in relation to landmarks and navigation buoys, for example, exceedingly easy. It also gives time of day, distance travelled and actual position co-ordinates, and can be linked to a VHF radio to meet the new small-boat navigation and positioning requirements.
For temporary installation on a borrowed RIB, we used a transducer mounted to the transom with a suction cup. The side-imaging function takes in a view of 180°, and you can alter the range according to depth of water.The dark part represents depth to the seabed. Then the software writers have unravelled the signal to take account of perspective and give you a picture (complete with sonar shadow) of objects that might be lying proud of the seabed.
Spot something, and you can not only mark the spot but record the image to an SD card.Magic! Modern divers don’t know they’re born!
