San Carlos Scuba Diving

News and Views

It is unlikely that a scuba diver in the Sea of Cortez will encounter a more alien and ornate decapod than the Cortez Barrel Shrimp, Gnathophyllum panamense. Also known as the Spotted Bumblebee Shrimp, this organism is difficult to confuse with any other Gulf of California shrimp species.

A downright beefy and glossy carapace is punctuated with large red or orange spots and smaller white polka dots. Accentuated by purple walking legs and white or yellow chelipeds and tail, the Cortez Barrel Shrimp appears to be an amalgam of highly disjointed parts.

Cortez Barrel Shrimp, Gnathophyllum panamense

Despite a wide range throughout the Sea of Cortez, from the tide pools of Puerto Penasco to the dive sites of Cabo San Lucas, scuba divers rarely sight the Cortez Barrel Shrimp. The ornate coloration of this shrimp is an excellent example of disruptive coloration and the bright splotches of color actually make the shrimp difficult for predators to visualize.

During the day, the Cortez Barrel Shrimp is reclusive and hangs on the undersides of rocky caves and caverns, or more commonly, underneath small rocks in rubble fields. Scuba divers most often catch glimpses of this beautiful creature during night dives when it emerges to feed. Little is known about the natural history of this shrimp. It has been reported to be a generalized omnivore, although it has also been reported to clean parasites off of fishes, as well as to consume the tube feet of echinoderms. While it is possible that this shrimp is more generalized than other members of the family Gnathophyllidae, it seems unlikely that this shrimp would be substantially different in diet than its kin, which are all starfish specialists.

Fall diving in San Carlos has been nothing short of spectacular this year. One of the most interesting of the sightings this year has been of one of the most secretive denizens – the Pacific seahorse, Hippocampus ingens. This is the only seahorse found in the western Pacific Ocean and Gulf of California. It is also one of the world’s largest seahorses reaching a length of 30cm (1 foot!)
Pairs of these beauties have been found at several dive sites throughout the summer. One particular pair of seahorses has inhabited the same spot at San Antonio Point all summer long and scuba divers have witnessed dramatic courtship displays and even frequent pregnancies of the male.
Although the Pacific seahorse is primarily a nocturnal species, scuba divers who patiently observe from a distance can also see and even hear the seahorses “snicking” at the passing clouds of mysid or possum shrimp that form the basis of their diet.

A pair of Hippocampus ingens at San Antonio Point, San Carlos, Sonora, Mexic0

Even when you know right where they are, seahorses can be hard to spot while scuba diving. Seahorses are masters of camouflage.

Fall is without a doubt one of the best times to scuba dive in San Carlos. The weather is mild and water conditions are superb. Warm water and great visibility!

With San Carlos water temperatures reaching into the 80’s and the clear blue water of summer arriving, more people will be considering deep dives. While most of the marine life will be found on shallower dives, there are a few organisms that are more prevalent at deeper depths. One in particular is the spectacular longnose hawkfish, Oxycirrhites typus.

Related Species
Familiar to most scuba divers in the Sea of Cortez are the Giant Hawkfish, Cirrhitus rivulatus, and the Coral hawkfish, Cirrhitichthys oxycephalus. The giant hawkfish is a large (to 20 inches, 520mm), green and brown mottled fish that is usually found in water that is shallower than 20 feet. The coral hawkfish is a smaller hawkfish that is usually less than 3 inches, 76mm, in length and white with red or pink polka dots.

The Longnose Hawkfish, Oxycirrhites typus
Unlike it’s more common relatives, the longnose hawkfish is rarely observed, partly due to the depths at which it is found, and partly due to exceptional abilities of camouflage. But for a careful observer, the difficulty in spotting one is worth the effort. Underwater photographers travel around the world to get a shot of one, but we have these beautiful fish in our own backyard.

With a striking red plaid coloration this fish has an immediate wow factor. What really sets it apart is the extended snout that it uses to pick small crustaceans off of the corals that it lives amongst. Found among the branches of black coral and gorgonians, the red coloration of longnose hawkfish fades at deep depths where reds are filtered and only blues remain. But bring a flashlight along and scuba divers will be able to see the brilliant colors of this fish in all their glory.

Hawkfish Habitat
Longnose hawkfish are rarely observed at depths shallower than 90 feet and become increasingly abundant as depths approach 150-175 feet. Even in these deeper depths they are not considered common. With persistence and bit of luck, they are spotted from time to time at Isla San Pedro Nolasco at depths ranging from 85-130+ feet. They are most often seen over small patch reefs that are surrounded by sand flats, or among the branches of the black coral colonies that are common at deeper depths. Both Northpoint and Southpoint have a smattering of these fish. Longnose hawkfish are even more plentiful along the Baja coast beginning at Isla Tortuga and south to La Paz and Cabo San Lucas.

Finding Longnose Hawkfish
To spot longnose hawkfish approach deep patch reefs and black coral colonies slowly. Move quickly, and the fish will startle and dive for cover, but if a scuba diver moves with care the fish will usually allow a close approach, relying on their camouflage for protection. Bring a flashlight to help you spot these beautiful little fish. The blue light at depth makes them blend into the background, but when illuminated by a flashlight, their reds will pop out of obscurity. Pay close attention to your gauges while hawkfish hunting. Both air and no-decompression time run out quickly at these depths.

The months of April and May are traditionally the transition period for water temperatures in San Carlos, Mexico. As the Sea of Cortez moves from its winter circulation patterns to summer currents, dramatic changes occur beneath the waves. The nutrient rich water of winter mixes with the warm equatorial water that invades the Gulf of California each spring. Combined with longer sunny days, this cocktail creates a veritable explosion of photosynthesis that fuels the Sea of Cortez.

Scuba divers will find that water conditions are very hit-or-miss with regard to visibility and temperature, but top-notch with regard to marine life. As the nutrient cycle ebbs and flows, scuba divers may experience pea-soup conditions one day as a plankton bloom occurs, and 50+ feet of visibility the next as the nutrients are locally exhausted, and as plankton is consumed by filter and suspension feeders.

Current water temperatures in San Carlos, Mexico are teetering at the edge of 70 degrees. Scuba divers in San Carlos may still find pockets of water in the mid 60’s, especially inshore, but there is a solid wall of water in the mid 70’s that is steadily edging its way north.

While clear blue water of summer is still over a month away, this is a great time to dust off a mid-weight wetsuit and experience scuba diving in the Sea of Cortez during a remarkable transition. Every dive will be packed with life, and this time of year is a macro photographers dream. Tons of oddball invertebrates are out and the plankton induces spawning and mating behaviors in many of these unusual creatures.