Large Pelagics Tag Recapture Reporting

In order to manage pelagic predators it is important to understand movements and behaviors from which factors such as stock structure and essential habitat can be determined. The Southwest Fisheries Science Center has employed a number of different approaches to characterize and quantify movements and behaviors in billfish sharks and tuna including conventional and electronic tags. These approaches allow us to follow these predators when they are out of sight, below the surface and/or across the oceans. Conventional tags are inexpensive and can be deployed in large numbers although you only obtain location information at the beginning and end point. Electronic tags are more expensive, however, with the data they provide, scientists can recreate the entire track in three dimensions. Both methods have their place and provide invaluable insight into the movements and behaviors of pelagic predators that can travel 1000s of km to feed or spawn.

Billfish Tagging

From 1969 through 2021, the Southwest Fisheries Science Center provided conventional billfish tags to individual anglers, charter boats, and tournaments in all oceans. Participating anglers also received the International Billfish Angler Survey, which compiled information on recreational billfish catch and fishing effort by location. Trends in angler days on the water and catchtracked over a 52-year time period provided a measure of relative abundance as well as patterns in effort. The primary species tagged over the course of the program included Pacific blue marlin (Makaira nigricans), black marlin (Makaira indica), striped marlin (Kajikia audax), Pacific sailfish (Istiophorus platypterus), shortbill spearfish (Tetrapturus angustirostrus), and swordfish (Xiphias gladius). The results of the Cooperative Billfish Tagging Program can be found in the annual SWFSC Billfish Newsletter webpage.

Shark Tagging

The Southern California Bight is a foraging habitat and nursery ground for various pelagic shark species. Researchers at the Southwest Fisheries Science Center have conducted research cruises in which thresher sharks (Alopias spp.), shortfin mako sharks (Isurus oxyrinchus), and blue sharks (Prionace glauca) were tagged with satellite tags and conventional tags. Additional efforts have focused on tagging basking sharks. The satellite tags allow us to characterize their species specific distributions, behaviors, movements, and essential habitat.

Tagging efforts also included research into age and growth, a critical component of stock assessments. The vertebrae of many tagged sharks were injected with oxytetracycline. Oxytetracycline is a fluorescent marker that deposits where new calcification is occurring at the time of injection and makes a fluorescent time mark in the vertebrae that can be examined in relation to new vertebral growth when a fish is recaptured. Our age and growth research is dependent on the reported recapture of these tagged sharks. If you captured a tagged shark, a reward is offered in exchange for recapture information and shark vertebrae.

Tuna Tagging

Since the 1970s, the Southwest Fisheries Science Center has collaborated with the American Fishermen's Research Foundation in tagging studies of North Pacific albacore (Thunnus alalunga). Through these studies we have learned that juvenile albacore (2 to years of age) can make trans-Pacific migrations, swimming between Japan and the West Coast of North America.

A $500 reward is offered for the return of an albacore tagged with an archival tags to the Southwest Fisheries Science Center.

Albacore Tagging Reward Brochure

Reporting Recaptured Tagged Sharks, Billfish, or Tuna

If you capture a billfish, shark, or tuna tagged with a Southwest Fisheries Science Center tag, a reward (see below) is offered in exchange for the recapture information,and the tag number. For sharks injected with oxytetracycline the vertebrae must be included:

Tag number and angler name (The tag number is indicated by "A0######", i.e. "A089287")
Recapture date, country, and longitude and latitude
Species and capture gear type
Fish length (centimeters or inches), length type (fork length, lower-jaw-to-fork-length, eye-to-tail, etc.), and weight (kilograms or pounds)
Fish sex when possible