26/12/2023
While everything, from ploughshells devouring blue bottles, crabs scuttling across rocks and Nudibranchs gliding over algae, is exciting to see on the Moonlight Meander, without a doubt, the sighting of an octopus is a universal highlight for our guests.
Watching them hunt in the rock pools, investigating the crevices for prey, or pouncing on a scuttling crab, skin flaps between its arms flared like a throw net has everyone spellbound.
Sadly, over the past 12 months, we have seen a steady decline in octopus due to over harvesting. The legal limit for someone with a fishing permit is for 2 per person per day. Sadly, we regularly witness families on a daily outing harvesting octopus, while within their limit, in excess of what they can realistically eat.
In December 2022 we would regularly count between 30 and 40 octopus in a 3 hour period. By the end January 2023, the count dropped to between 3 and 5 octopus per three hours, testimony to the extent of the number caught during season.
Now, at the end of December 2023, we are only seeing between 5 and 8 per three hours, most of which are juveniles, an indication that the population at Gericke's Point is being over harvested and has not being allowed to recuperate.
As apex predators in the intertidal zone, particularly in rocky intertidal zones, octopus, like all other apex predators, have a vital role in maintaining marine biodiversity and productivity.
In the past months, I have constantly been asked why the Gericke's Point rock pools look 'less vibrant' than they have in the past.
The reality is a combination of factors, but one of the largest contributing factors is the small population of apex predators. Without octopus, the herbivore populations increase, devouring the algae as they do. Once over grazed, then the herbivore population crashed (top Shells, alicruekel, sea urchins and limpits). Without herbivores, the carnivore population (whelks, starfish) declines. As such, the pools lose their biodiversity and are visually degraded.
Comparative studies of adjacent intertidal zones, one within a MPA, show that there is are robust reefs with incredible biodiversity, large reef fauna and higher density.
It is time for us, locals and visitors, to realize that, yes, we are indeed having a significant impact on the biodiversity are Gericke's Point.
Fortunately marine populations have a remarkable capacity of recovery and all that is required is a period of rest, between 4 and 8 months.
In fact, a study by Dr Jan de Vynk, demonstrates that a cycle of breif harvesting followed by a rest period of 8 weeks increases the yield per hectare in the intertidal zone.
Octopus live for about 2 years. They mate when they are about 18 months, after which the male dies. The female then searches for a suitable lair for a nursery to lay her eggs.
She cares for them, constantly cleaning the eggs to remove pathogens and venting oxygenated water over them. Then, after 3 months, as the eggs start hatching, she dies. During this 3 month period,she does not eat.
She lays tens of thousands of eggs, most of which are eaten in the first few weeks after hatching.
The video below is of a female search for a nursery lair. Once in the lair, if caught by a fisherman, the eggs will mostly perish from pathogens, killing more than just one octopus.
