For O.C. man, it was day of the dolphin

A kayaker encounters a group of Risso's dolphins off Corona del Mar Sunday.
A Risso's dolphin takes a leap Sunday perhaps a quarter mile off Newport Beach.
A group of perhaps 20 to 25 Risso's dolphins seemed to perform for the camera off Newport Beach Sunday.
The heavy scratch marks on the backs of Risso's dolphins are likely from two possible sources: bites from other Risso's, and their prey, such as Humboldt squid, that can rake the dolphins with their beaks when attacked.
Risso's dolphin in a calm moment off Newport Beach Sunday.
Risso's dolphins, like the one shown here, were unseen in local waters until 1982, according to Orange Coast College marine science professor Dennis Kelly.
Risso's dolphins at play off the Orange County coast Sunday.
Some in a group of perhaps 25 Risso's dolphins just off Newport Beach Sunday. The species is fond of hunting for squid.
Risso's dolphin gets an eyeful Sunday, perhaps of the photographer taking his picture.
A local photographer caught sharp images Sunday of a group of Risso's dolphins just off the Newport Beach coast.
An "offshore" bottlenose dolphin takes a leap out of the water off the Laguna Beach coast Sunday.
"Offshore" bottlenose dolphin re-enters the water after becoming airborne.
A Laguna Niguel resident captured dolphins at play Sunday off the Orange County coast.
Bottlenose dolphin takes a twisting leap off the coast of Newport Beach Sunday. It is likely an 'offshore' bottlenose, a bit larger and more sleek than the 'coastal' bottlenose variety, said Orange Coast College marine science professor Dennis Kelly.
A Risso's dolphin leaps out of the water off Newport Beach Sunday. This species 'melon,' or echolocation organ in the head, is split, possibly allowing more acute sensing abilities than is true for bottlenose dolphins.

By Pat Brennan | Orange County Register

November 29, 2011 at 12:45 p.m.

Dolphins leaped and performed off the Orange County coast Sunday for William Nelson of Laguna Niguel, who captured the animals in action as he rode past in a boat.

Nelson first encountered a group of perhaps 20 to 25 Risso’s dolphin about a quarter mile off Newport Beach.

It’s an odd species unseen in local waters before 1982, said Orange Coast College marine science professor Dennis Kelly.

Over time, the Risso’s might have chased away populations of pilot whales, which also eat squid and were once common, but whose local numbers have since dropped.

Later in the day, Nelson came across what Kelly identified as “offshore” bottlenose dolphins, a group that is larger and more sleek than the “coastal” bottlenose.

These were perhaps two miles off Laguna Beach.

A few bottlenose can sometimes be found mixed in with groups of Risso’s, and the Risso’s sonar abilities could be the key.

Both have “melon” organs in their heads that are used to find prey by echolocation. But in Risso’s, the melon is split, which might allow a kind of “Doppler sonar,” making them more sensitive, and better at finding squid, than the bottlenose dolphins, Kelly said.