I second D's request for a journal on which species you see- especially if you can also record numbers and moon phase (zeroes are also very useful for setting the scale of your observations). You could show some really interesting patterns, and potential for seasonality. It would be great if you could 1) standardize some of your observations- say keeping track of dive time, using a similar search pattern (and not just swimming to the spot where you know an individual already is- as tempting as this is!); 2) measure them (a cutting of a transect tape/knotted string work fine) to measure mantle length (from between the eyes to the back of the mantle) and 3) sex ratio (the third right arm of males is modified, has a groove along the back edge and no suckers on the tip), 4) time/date of sighting, 5) habitat (the latter two helping to assess how much they may overlap/encounter each other/compete for food. and/or shelter).
This would be similar to the very useful "List of our octopuses" here on Tonmo, spearheaded initially by Nancy. I have found that list extremely useful and have certainly cited it.
It is up to you if you want to measure and sex them- measuring would require handling, and even with gloves in theory there's still a chance you could get bitten. Amphioctopus is the sister group to blue rings. Based on the fact that they are heavily fished and consumed throughout SE Asia, they are not thought to be deadly like blue rings. But for most species we know nothing of their bite...except A. mototi which is known to have a powerful venom.
The densities you are seeing are truly remarkable for animals that size. Something very interesting could be going on there, either in terms of mating aggregations or predatory release. You say it's a marine reserve? How intact is the fish community?
Don't worry D- I've never thrown a tomato here, and don't plan to!
as well!
