Dave Holts, off Ucluelet, British Columbia, Canada. – We’re here to catch at least 10 blue sharks greater than six feet long, and tag them with satellite and archival tags. This is part of a blue shark distribution and habitat study. In 2002, the National Marine Fisheries Service at the Southwest Fisheries Science Center in La Jolla joined forces with Tagging of Pacific Predators to study the migratory behavior of blue sharks.
[Ed. note: Researchers from NOAA’s Southwest Fisheries Science Center in La Jolla went on four shark-tagging expeditions this summer. Three of the expedition leaders sent TOPP daily blog entries. Dave Holts was able to send his after the expedition. This week we’re featuring his 10-day expedition, which occurred in July, in four blog entries.]
At that time, 33 blue sharks were tagged off southern California and northern Mexico. This year, we’re tagging blue sharks at the northern extent of their range off Vancouver Island, British Columbia with researchers at the Pacific Biological Station, Department of Fisheries and Oceans in Nanaimo. We also want to collect DNA for population studies and we plan to inject sharks with oxytetracycline to help us understand sharks’ growth rates and aging.
SPOT tags – satellite position only tags -- report a shark’s location and time to satellite receivers every time the shark comes to the surface and its dorsal fin breaks the surface of the water. This way, we can monitor the movements and locations of the shark for up to a year. The archival pop-up tags (PATs) have a series of sensors that collect data on swimming depth, water temperature and location on a RAM memory chip. These tags can be programmed to release from the shark at any time up to about a year. Our tags are all programmed to release after 275 days after being place on a shark. So, this tag will detach from the shark in 275 days and start sending that information to the Southwest Fisheries Science Center via the Argos satellite system. These data help scientists identify and describe the shark’s natural habitat and migration patterns.
On Wednesday, July 18, I left San Diego for Nanaimo, British Columbia to meet Dr. Gordon (Sandy) McFarland to begin the blue shark survey off the south end of Vancouver Island. When I arrived, Sandy was there, but my luggage wasn’t. On Thursday, after my luggage and tagging gear finally arrived, we proceeded to the Canadian Coast Guard vessel Neocaligus in the port of Ucluelet on the west side of Vancouver Island. There I met Sandy’s colleague Dr. Jacquelyn King, who was to assist us in the tagging expedition. We spent the afternoon preparing gear and equipment for our first planned fishing set Friday morning.
On Friday, we left port at 4:30 a.m. and proceeded to the fishing grounds 30 miles west of Barkley Sound, Vancouver. The seas were 5 to 6 feet with wind-blown waves of 2 to 3 feet. It took me way too long to get my sea legs and, yes, I was seasick for the first time in many years. Uck! You know you’re seasick when you want to die and you’re afraid you won’t.
Undaunted by this, we set out 75 hooks on a one-mile long cable longline and soaked it for 45 minutes before hauling it back in. The photo, below, shows the longline going off the back of the ship. We bait each hook and attach it to the line as it rolls out.
We put streamers on the gear to keep the birds away. Fortunately, they weren't interested in getting too close to the boat.
We caught a blue shark on the first hook.Yea! Gunna be a great trip, I figured. On the second hook…another blue shark…a big one over 6 feet long. Two hours latter, we had measured; tagged, collected DNA, injected oxytetracycline and returned 51 blue sharks to sea. Two of these were over 6 feet long, so we placed satellite tags on them.
Fortunately for me, Capt. Roger Williams said we had to return to port because the sea state was expected to get worse. I told him it was already worse and I was dying. He chuckled and said, “Yes, but we won’t be able to hold on in the weather expected in a couple hours.” After we tied up back in Ucluelet, I started feeling much better.