By Dave Huckle
From October 2000, we have been tagging Nile perch caught from Lake Nasser. Here Dave Huckle, the program's initiator gives details.
Why are we tagging Nile perch?
The program has been developed to give us a better understanding of Nile perch in terms of growth rates, movement, seasonal migrations etc. The previous catch-and-release policy ensured the preservation of fish stocks but did not provide any way of monitoring the fish. The tagged fish now has a unique identity rather than just being an 80-pounder, for instance, that swims off and may, or may not, be caught again.
How does the program work?
The program is restricted to fish of 75lb and above. (We simply couldnt afford to tag every fish caught!)
When a fish is tagged the details are entered into a database which records the vital statistics of the fish, the location and method of capture and the angler.
This information can be used to produce a variety of reports which will not only give anglers valuable feedback on catch rates and fishing methods but will also provide valuable scientific data.
How are the fish tagged?
Each fishing boat carries a tagging stick and a set of individually numbered tags.
The tags are made of hygroscopic nylon, originally developed for use in artificial organs and joints in humans. The nylon encourages tissue bonding, thus avoiding the problem of tag shedding seen in the early billfish tagging programs.
The African Angler guide in each boat has been trained to tag perch without damaging them. The tag is inserted at an angle of 40-45 degrees (facing backwards) under a scale. It should be placed below the dorsal fin (but not so low as to hit the backbone). The tagging stick is designed to penetrate to a maximum depth of 1.75 inches and is simply pushed swiftly into the side of the fish, given a twist to lock the tag and removed. The whole process takes just seconds.
What information is recorded?
Every guide will have a supply of tagging forms. It is vital that all sections are completed. It is vital that all sections are completed. If we dont have complete data, we cant give anglers any feedback!
All we need is the tag number, the fishs weight, length and girth (measured around the hump) and the lure type and color used plus date, time and location of capture. To establish the location each skipper has a map of the lake. You can either use the map to establish the grid reference, or simply mark the place on the map with the tag number. Any additional points that anglers feel may be relevant can be entered in the Comments box.
What about recaptures?
You dont need to tag out or re-tag! Simply record the tag number and mark the recapture box. Record all other data as per usual. Its quite sad but well probably get very excited about recaptures and may even have a bit of a party.
What will we do with the data?
From the anglers perspective, well use the data to produce reports for the African Angler newsletter. Youll be able to see if your tagged fish are recaptured and, hopefully, well have more of an insight into what they get up to in the depths of the lake.
Footnote: Dave Huckle would like to thank Dave Bird, also the UK Shark Tagging Program (www.ukshark.co.uk), whose organizers, Sue and Jeri Drake, provided invaluable help and advice towards setting up the Lake Nasser Nile Perch program.
*This article courtesy of The African Angler Magazine, Summer 2000 No. 8 issue
Last Updated: June 15th, 2011