WHY DO WE NEED A "PRIORITY SPECIES" LIST?
Why do we need a "Priority species" list?
"Some of our taggers are disappointed when we tell them that they can only tag fish species on our priority species list and not just any old fish they catch. There are a number of important reasons for this. "
Some of our taggers are disappointed when we tell them that they can only tag fish species on our priority species list and not just any old fish they catch. There are a number of important reasons for this.
Firstly because we import our tags from Hallprint© in Australia, tags now costs about R12 each and we want those tags to be used on important species that we need information on and not wasted on species which are of relatively little scientific interest.
Secondly, there are a number of fish species which research has shown simply do not hold tags well or are very susceptible to injury and exhibit low survival following a tag and release event. Good examples would be blacktail and slinger. Many thousands of blacktail were historically tagged in the De Hoop and Tsitsikamma tagging projects and results showed that apart from them generally being relatively small fish (with few of them being greater than the minimum tagging size of 30 cm fork length), most blacktail would shed their tags very quickly (with evidence of tag scars on recaptured individuals) and were thus not ideal species for a tag and release study using dart tags. Similarly, past research on slinger has shown that this species is extremely susceptible to the effects of barotrauma (trauma caused as a result of pressure reduction when brought up from deep water) and thus do not survive well when tagged and released by members of the public.
A third reason is that in the case of some commonly caught species such as lesser sandsharks, diamond rays and blue rays, many thousands have been tagged but we have had remarkably few recaptures suggesting that either the fish themselves are succumbing to predation after tag and release or the tags themselves are being shed. Either way, future focused tagging on these species using dart tags, is unlikely to produce meaningful results. There are also certain species which it is now illegal to tag such as great white sharks. Other species such as West Coast Steenbras which are mainly caught in Namibian waters and are thus outside the jurisdiction of the ORI-CFTP. Other species are generally too small (e.g. Cape stumpnose and steentjie), very susceptible to handling injury (e.g. bonefish and dorado) or simply so abundant that efforts to tag them have largely proved unsuccessful in terms of getting a useful number of recaptures (e.g. Cape snoek and panga).
Because of the above mentioned reasons ORI scientists periodically evaluate the species on our priority tagging list and we ask our taggers to try and focus their efforts on these target species.