By Dr Bruce Mann
The 50th Pondoland Marine Protected Area (MPA) fish monitoring field trip was undertaken from 26-27 October 2020. This project has been running since 2006 and primarily uses controlled research fishing and tagging as part of ORI’s ongoing investigation into the effectiveness of the MPA. ORI senior scientist, Dr Bruce Mann leads the team and funding has been received in terms of a contract with the Department of Environmental Affairs, Forestry and Fisheries (DEFF).
CONTROLLED FISHING SURVEY
Fishing is conducted using standardised bottom traces with barbless circle hooks. All fish caught are carefully handled and released unharmed. Overall, 80 fish (54%) were caught in the no-take area, which amounted to 8.89 fish caught per angler per hour. Fishing in the exploited area was also reasonably good and 68 fish (46%) were caught amounting to 7.56 fish caught per angler per hour. This was after the same amount of fishing effort in both areas in two successive days of fishing with very similar weather conditions. The team recorded a total of 17 fish species with 11 species caught in the no-take area and 15 species in the exploited area. Species composition was dominated by Natal seacatfish (22), slinger (19), scotsman (16) and yellowbelly rockcod (9) in the no-take area, while catches in the exploited area were dominated by Natal emperor (17), scotsman (13), halfmoon rockcod (9) and slinger (8). As usual, the average size of fish caught was generally much larger in the no-take area. The biggest fish caught during the trip included three beautiful black musselcracker of 790, 770 and 695 mm FL (14.0, 12.9 and 9.5 kg respectively) with two caught in the Mtentu area and one in the Mnyameni area.
A total of 66 fish were tagged overall with 31 tagged in the no-take area and 35 in the exploited area. Scotsman was the most common species tagged (n=21), followed by black musselcracker (n=9), and slinger (n=7). Over the two days the team recaptured a remarkable 17 fish with 14 coming from the no-take area and 3 recaptures from the exploited area. The fish with the greatest distance moved was a scotsman that moved 708 m in the Mtentu sampling area. All other recaptures moved a lot less with the average distance being a mere 173 m from where they were originally tagged. This indicates the high level of residency of most reef fish. The fish with the longest time at liberty was a Natal seacatfish that had been free for 9.3 years and during this time had been recaptured no less than six times! The team also recaptured a scotsman, a halfmoon rockcod and a flapnose houndshark all of which had been free for 8.7 years. Since the last field trip in July, two tagged black musselcracker have been recaptured outside the MPA, one off Glenashly (travelled 260 km and free for 5.3 years) and the other off Mtunzini (travelled 298 km and free for 7.2 years). The movement and growth rate information obtained from these recaptures is invaluable.
During this field trip the team managed to tag another three big black musselcracker bringing the total to eight black musselcracker tagged with acoustic tags. They also managed to tag another four flapnose houndsharks with acoustic tags bringing the total to 10. The dusky shark was also tagged with an acoustic tag as part of another project monitoring the movement behaviour of this species. It is going to be very interesting to see the movement behaviour of these animals in the future. The next roll-over and download of our five acoustic receivers in the Pondoland MPA is scheduled for June 2021. This aspect of the project is being done in collaboration with the Acoustic Tracking Array Platform (ATAP) hosted by the South African Institute for Aquatic Biodiversity (SAIAB).
Since April 2006 (with a break between 2016-2017), the ORI team have conducted extensive monitoring in the Pondoland MPA using multiple methods including research fishing, tag-recapture, underwater visual census, baited remote underwater video, and monitoring movements of fish tagged with acoustic transmitters. From this research, it is very clear that the no-take area in the Pondoland MPA is providing an important refuge for many overexploited fish species. Many popular linefish species such as scotsman, slinger, yellowbelly rockcod, black musselcracker, etc. are much more abundant and of a much greater size in the no-take area than in the adjacent exploited area. Some species such as black musselcracker are known to spawn in this area and the increase in the number of juvenile black musselcracker in the exploited area reported by local ski-boat anglers bears testimony to the potential of the no-take area to seed adjacent areas. Similarly, over time several species of fish, especially scotsmen and slinger have been observed leaving the no-take area and moving northwards up the coast presumably to spawn in warmer waters. This provides further evidence of spillover from the MPA, which is helping to enhance fish populations in the exploited areas along our coast and providing direct benefit to fisheries.