The Great Fish Guestimation Competition
by Brent Lewis
âFine.â He replied âWhat do you have in mind?â
âWell, I have these plastic fish…â
And so began the first Great Fish Guesstimation Competition. The plastic fish I had actually belonged to Anjali, who is based at the Island Bay Marine Laboratory, and who had laboriously cut out the silhouettes of 17 fish as part of her PhD research. She needed to undertake some calibration dives to determine how accurately divers are able to estimate the size of fish whilst swimming along a line 25 metres long.
I arranged the competition for the first Saturday of June, being close to the first official day of winter. As luck had it the wind was a mere 50 knots or so. Nothing really. Oh sure, we had to make certain things like gloves and hoods didnât blow away, but we donât consider it windy until tanks and weight belts start disappearing. Any wind thatâs not strong enough to shift a weight belt isnât worth mentioning!
So, a hardy group of divers turned up on Wellingtonâs south coast for the competition. The south coast is only 10 minutes drive from the centre of the city, and offers some really good shore dives with interesting terrain and lots of things to look at including cod, tarakihi and butterfish, stingrays, crayfish, the occasional nudibranch and wonderful jewel anemones. On this occasion though, all eyes were on 17 plastic fish attached to lead weights and spread out in an unrealistic fashion along the bottom.
I loaded the fish into this handy spring loaded bag that I have for collecting any litter I might find whilst on a dive, and headed out into the bay with a dive flag and a line reel. Securing the flag in four metres of water I descended and laid out 25 metres of line, spreading the fish either side of the line. The idea was that contestants would swim along the line and estimate the species and size of the fish and note this on a slate. I left my security man on the surface with a long pole with which he could poke any cheaters who may have brought a tape measure and a fish ID slate. In truth he had borrowed someoneâs drysuit, the softie, and didnât have enough weight to descend.
Not only did we have a mere 50 knot zephyr, we also had very handy torrential rain to induce people into the water. The size estimation wasnât too bad, but the species identification was terrible. To be fair though, without their colouration and markings it was hard to work out what they were.
Once everyone had finished their guesstimation they took off for a tour around, as the viz was quite good. We were diving in quite a nice area with gravel bottom and rocky reefs providing homes for encrusting sponges, anemones, kina and, of course, fish, so it was well worth the effort of getting out on a winterâs day. Eventually I coaxed all the divers out of the water, who then got saturated as they changed into their âdryâ clothes. I retrieved my plastic fish and we all returned back to New Zealand Sea Adventures at Tahiti Bay where Tony had hot soup waiting and some prizes for first place and all the runners-up, which was everyone else.
We supped our soup around the heater and told lies about how good our estimation was while we agreed it was great to be a diver. So the lesson is, donât sit around all winter waiting for the rain to stop so you can mow the lawn. Get out there and go diving and have some fun.