ORI celebrates 30 years of citizen science

ORI celebrates 30 years of citizen science

  Wednesday, 2017/07/12
 Stuart Dunlop

"The Oceanographic Research Institute celebrates 30 years of citizen science through its cooperative tag and release project"

A yellowfin tuna tagged off Cape Point was recaptured just under two years later, off the Seychelles, having travelled an incredible distance of +5 100 km. This means that the fish swam a minimum of 7.3 km per day, assuming it travelled in a straight line! Of greater significance is the fact that this yellowfin tuna has shown us there is some connectivity between tuna populations that occur in the Atlantic Ocean off South Africa and those found in the Indian Ocean around the Seychelles. This finding is invaluable, particularly for the future management of these fish populations that were once thought to be separate fish stocks. This tuna recapture is also the furthest recorded distance moved by any fish tagged on the Oceanographic Research Institute’s Cooperative Fish Tagging Project (ORI-CFTP).

The ORI-CFTP was the brain-child of past ORI Director Rudy van der Elst. Rudy realised the potential for a well-managed cooperative fish tagging project to generate much-needed data on linefish and, being spurred on by a growing concern amongst anglers of poor fish catches, the ORI-CFTP was launched in 1984. After 30 years, this project is still going strong and is undoubtedly one of the most enduring and successful environmental projects of its kind in South Africa. It involves the cooperation of conservation-conscious anglers (i.e. anglers who voluntarily tag and release their fish) and the marine angling public at large, who report the majority of the recaptures (i.e. a fish that is recaught with a tag in it) to ORI. Despite the voluntary nature of this project, the tagging of fish still has great scientific merit, allowing us to learn more about the movement patterns, growth rates, mortality rates and population dynamics of our important linefish species. This information is extremely valuable and is used by scientists and managers around the country for policy and decision making on linefishery management. Despite the large quantity of important scientific data collected by this long-term project, the tagging project has also made a major contribution towards changing the ethics of anglers with regard to catch-and-release, which undoubtedly goes far beyond the pure scientific value of the data collected. Not only do anglers now have a reason to capture and release a fish, they are in actual fact contributing to a better understanding of the biology and ultimately the conservation of that species. This added bonus goes a long way in improving angler awareness about our marine linefish species, as well as contributing towards sustainable fishing.

There are many different types of tags used on different fish species (e.g. PIT tags, satellite tags, acoustic tags, archival tags, etc.); however, the most common method is conventional tagging and involves the use of external dart tags, which are the preferred type used in the ORI-CFTP. Each tag consists of a monofilament vinyl streamer attached to a plastic barb, much like a miniature version of a spear from a speargun (Figure 1). Each tag is inscribed with a unique alpha-numeric code (e.g. D123456) and contact details (i.e. email address, cell phone number and postal address). Tags are generally inserted with a sharp, hollow, stainless steel applicator, into the dorsal musculature of a fish or shark, although this may differ in certain fish species (e.g. rays). Upon initial tagging (and subsequent recapture of a tagged fish) anglers record the following information: fish species, length (fork or total), tag number, exact locality and date. The use of external tags by the ORI-CFTP is particularly favourable as it is relatively cheap compared to other tagging methods, relatively little training is required to insert tags, no software is required to download information from each tag, and the tagging equipment is very basic. This allows a relatively large number of fish to be tagged at little cost and allows citizens who are not trained scientists to be involved, similar in some respects to the South African Bird Ringing Unit. However, considerable attention has been focused on ensuring that the best available tag and tagging equipment is used and that our taggers are shown how to handle and tag fish correctly, in order to minimize post-release mortality.

Currently some 6 077 members have joined the ORI-CFTP since 1984 and they have accounted for the capture, tagging and release of an incredible 325 333 fish, mostly in South African coastal waters, but also occasionally in Mozambique and Namibia. Note should be taken that this represents 325 333 fish that were released to ‘fight another day’ and hopefully reproduce for future generations. Of the fish tagged, 20 655 (6.3%) have been recaptured and reported to ORI. Our top five fish tagged include: galjoen (64 868), dusky kob/kabeljou (20 392), leervis/garrick (16 388), dusky sharks (14 395), spotted grunter (13 090) and copper/bronze-whaler sharks (9 706). Unfortunately, a large proportion of recaptured fish are not reported to ORI, which would, with greater awareness, undoubtedly increase the recapture rate substantially. If you see or hear of any angler who has caught a tagged fish, please offer to assist them in recording the relevant information (tag number, species, correct length measurement, exact locality, date, angler name and contact details, and whether the fish was kept or re-released) and even offer to send the information in to us on their behalf (email: oritag@ori.org.za / Tel: 031 328 8222 / sms +27 79 529 0711).

Over the past 30 years there have been some amazing recaptures reported to ORI. The fish species with the highest recapture rate is speckled snapper with 2 381 fish tagged of which a remarkable 929 (39%) have been recaptured, owing largely to its highly resident behaviour. Galjoen, our national fish, is the most tagged species on the project, with 64 868 fish tagged, accounting for 20% of the total number of fish tagged to date. Much of this is thanks to the efforts of the research team that has been tagging galjoen in the De Hoop Marine Reserve since 1987 and some avid taggers fishing along the Cape Peninsula. The longest recorded time free (the length of time a fish was at liberty between the initial tagging and first time recaptured) for a bony fish was for a red steenbras tagged in the Tsitsikamma National Park in 1989. This fish was recaptured off the Kei Mouth in the Eastern Cape in 2011, some 22.1 years later, providing strong evidence of the longevity of this species. Similarly, a ragged-tooth shark tagged at Southbroom on the KZN south coast in 1988 was recaptured in Mossel Bay in 2011, a staggering 22.6 years later and 1014 km away from its original tagging location. The most recaptured individual fish on the project is ‘Rocky’, a yellowbelly rockcod tagged in the Pondoland MPA just south of Port Edward, which has been recaptured no less than nine times on the same reef over a three-year period (Figure 2)! It is these incredible recaptures and the numerous others on the tagging database that make this project so exciting and beneficial.

We would like to express our sincere gratitude for the financial and administrative support received from the following organizations during the 30-year history of this project: the South African Association for Marine Biological Research (SAAMBR), Stellenbosch Farmers Winery (now called Distell) who generously funded the tagging project for 22 years under their Sedgwick’s Old Brown Sherry brand, the South African Nature Foundation which became WWF-South Africa, the Tony and Lisette Lewis Foundation and most recently the KZN Department of Economic Development, Tourism and Environmental Affairs (EDTEA), without which we would have been unable to continue this important project. Most of all, we would like to thank all of our past and currently active tagging members for their valuable contributions towards this project. David Hall (Hallprint© Australia) is thanked for his excellent service and on-going supply of high quality tags and applicators. Lastly, we would like to thank Rudy van der Elst for his foresight in developing this remarkable “citizen science” project long before the coining of the phrase; and to Elinor Bullen for running the project as ORI’s “Tagging Officer” for an incredible 27 years (1984-2011)! 

"Anglers contribute to 30 years of tag and release science." Read more