Over the last approximately 2 years, dead and rotting seals on Plett beaches have caused concern and not a little offence to residents and visitors.
The Plett environmental forums and the Bitou Beach Management department under the leadership of Mark Fourie, have been looking at the problem to find the best way to handle it, for the best natural environment and for the comfort of beachgoers.
The full report below has been submitted by Marine Biologist, Frikkie an der Vyver, MSc. Here are the main findings and recommendations.
Bitou Municipality will be taking cognisance of the findings as they work towards implementing the best solutions.
1) The low-level helicopter flight on 30 November 2019 may have caused disturbance at the colony leading to drowning of pups and subsequent strandings on Robberg beach, but this potential impact was minor compared to evidence of natural mortality most likely related to high easterly wind and swell.
2) There is emerging evidence of an increasing trend in pup production estimates at the Robberg seal colony, most likely related to a local increase in the availability of preferred prey (i.e. small pelagic fish), leading to an increase in body condition and therefore reproductive rates of females. A possible influx of breeding females from other colonies may also be a contributing factor and could be investigated in future using satellite tracking devices, if funding becomes available.
3) If observed trends in seal pup production estimates continues you can expect further increases in the numbers of carcasses washed ashore on Plett beaches in coming years.
4) Major municipal beach cleanup efforts should be scheduled after periods of high easterly wind and swell have passed, as such conditions appear to cast the highest number of carcasses ashore.
5) Continued boat-based counts of live newborn pups at the colony and land-based counts of carcasses washed ashore is crucial in studying the importance of seal birth rate as an indicator of ecosystem health and/or changes lower down in the food web, especially if linked to results from future diet analysis of adult seals.
READ THE REPORT HERE (PDF)
Frikkie van der Vyver, MSc
Plett Stranding Network: 079 463 4837 (to report marine mammals ashore, dead or alive)