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The 51st Pondoland MPA fish monitoring field trip

By: Dr Bruce Mann

The 51st Pondoland Marine Protected Area (MPA) boat-based reef fish monitoring field trip was undertaken from 21-22 January 2021. 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, Bruce Mann leads the team, with funding and logistical support from the Eastern Cape Parks & Tourism Authority (ECPTA) and SAAMBR, and acoustic tags and receivers provided by the South African Institute for Aquatic Biodiversity (SAIAB) and their Acoustic Tracking Array Platform (ATAP).

Fishing is conducted using standardised bottom traces with barbless circle hooks. All fish caught are carefully handled and released unharmed. Overall, 99 fish (60%) were caught in the no-take area, which amounted to 11.38 fish caught per angler per hour. Fishing in the exploited area was slower and only 66 fish (40%) were caught amounting to 7.33 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 13 fish species, with 9 species caught in the no-take area and 12 species in the exploited area. Species composition was dominated by slinger (33), scotsman (27), black musselcracker (17) and yellowbelly rockcod (11) in the no-take area, while catches in the exploited area were dominated by halfmoon rockcod (19), scotsman (11), Natal emperor (8) and slinger (7). As usual, the average size of fish caught in the no-take area were much larger. The biggest fish caught during the trip included a black musselcracker of 580 mm FL (5.5 kg), a yellowbelly rockcod of 628 mm TL (4.4 kg) and a scotsman of 630 mm FL (4.3 kg).

A total of 99 fish were tagged overall with 63 tagged in the no-take area and 36 in the exploited area. Scotsman was the most common species tagged (n=24), followed by black musselcracker (n=19), and slinger (n=18).  Over the two days the team recaptured a remarkable 14 fish with 9 coming from the no-take area and 5 recaptures from the exploited area. The 14 recaptures included 9 scotsmen, 2 yellowbelly rockcod, 2 halfmoon rockcod and 1 Natal seacatfish. The fish with the greatest distance moved was the Natal seacatfish that moved 431 m in the Mkambati sampling area. All other recaptures moved less with the average distance being a mere 187 m from where they were originally tagged. This indicates the high level of residency of most reef fish and their relatively small home range sizes. The fish with the longest time at liberty was the Natal seacatfish that had been free for 7.3 years and during this time had been recaptured twice. The team also recaptured two scotsmen that had been free for 4.9 and 2.7 years respectively. The movement and growth rate information obtained from these recaptures is extremely valuable.

During this field trip the team managed to tag another flapnose houndshark with an acoustic tag bringing the total number of houndsharks tagged to date to 11. The next roll-over and download of our five acoustic receivers moored in the Pondoland MPA is scheduled for June 2021.

Since April 2006 (with a break between 2016-2017), the 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 areas adjacent to the MPA reported by both shore and ski-boat anglers, bears testimony to the potential of the no-take area to seed adjacent areas. Similarly, over time the team have seen several species of fish, especially scotsmen and slinger 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.