When we first arrived in the Pacific Remote Islands Marine National Monument waters off Johnston Atoll we started plotting bottomfish sampling locations using topography, currents and the EK-60 fish finder to identify areas of interest. However this was altered during the field work because we encountered a lot of sharks during our fishing efforts. We later decided to target depth features with less fish abundance so we would have a higher probability of obtaining our samples without shark interference. See previous bottomfish research expedition post: http://bit.ly/17RGrdg
The sharks appeared to be Galapagos sharks based on surface sightings and “Go-Pro” camera video shots taken underwater from a submerged pole over the NOAA Ship Oscar Elton Sette’s side. Once we are back in Honolulu we will upload the videos to this blog for your viewing. We have some amazing footage that provided a huge surprise on the actual number of sharks present under the boat. One video showed at least 15 sharks circling at one time.
During one day of bottomfish sampling from the NOAA Ship Oscar Elton Sette we were operating on a one drop per station method. Typically we could get one drop down and recover fish but on the second drop the sharks were ready for us and either attacked our fishing line deep during retrieval or at/near the surface. Three Galapagos sharks completely devoured a hapu’upu’u that we brought to the surface; excellent “Go-Pro” video was taken of this event. The small boats were also plagued by shark activities.
Shark avoidance maneuver on the small boats
The small boat crew also had their hands full with the over-exuberant sharks. To avoid the problem of losing parts or all of the fish to the sharks, the small boat crew came up with a “shark avoidance maneuver”. Jamie Barlow explained that once sharks were spotted while reeling in a desirable bottomfish (determined by how the line feels during the bite), the small boat would have to maneuver to avoid loss of the sample. This could be accomplished either by speeding away with a high probability of losing the sample (fish busting the leader or tearing away) or going slow and losing the sample to the shark. To avoid either of these undesirable outcomes they considered several factors when determining actions to be taken on the small boat for saving the fish.
Every situation was different and the coxswain had to mitigate the risks and factor in these variables:
1. What is the load (weight) on the rod and reel (how big, how many)
2. Consideration of running the small boat down seas so the rod does not jerk the fish and release itself from the hole the hook would make in the fish’s jaw.
3. Be aware of the location of the sun glare (reflection of the sun off the water) and finish the maneuver so the small boat crew can see the sharks for the last critical 30 seconds of recovery
4. Consider heading to deeper waters where typically there was less shark abundance
5. How aggressive are the sharks?
6. Pull the line with the fish rapidly and safely into the boat without inviting the shark into boat as well
7. Whoever is pulling the line is experienced enough so that if the shark does grab the fish, they will hold that line firmly to bust the leader and prevent gear and hooks to be pulled backward by the powerful fish.
While calculating these variables, Jamie Barlow would conduct this maneuver as a spiraling left turn. Varying angles and speeds were balanced while being mindful of keeping the line away from the prop and bringing the fish coming out at an angle and a speed that prevents the shark from grabbing the fish. This was a tricky maneuver, but it worked for about 3-5 times, after which, the sharks wised up. The sharks had watched enough fish scoot passed them to learn that a bold burst of ambush speed would reward the natural predator with a tasty opakapaka or onaga. And once they got that bold the fishermen would have to tuck their tails between their legs and run a mile to a new spot and start the “small boat shark maneuver” all over again. See next bottomfish research expedition post: http://bit.ly/15VFlU8