Taxonomy

Rarity

The rock wrasse is one of the fish a snorkeler will actually see on a Southern California reef, month after month. It is a common resident of rocky reef and kelp from Point Conception, in Santa Barbara County, south to the border. Any productive kelp edge in the top 30 feet will usually turn up several. The IUCN Red List assessed the species as Least Concern in 2007, its status ever since. It is not a fishery target in any meaningful way. Pier anglers catch a few, most often from the Green Pleasure Pier at Avalon on Catalina Island and from a handful of Los Angeles County piers such as the one at Redondo Beach and the Paradise Cove Pier in Malibu. There is no directed commercial or recreational fishery. Nobody spearfishes them, because the fish tops out at about 15 inches and most are smaller than 12. What makes the rock wrasse feel scarcer than it is has more to do with recognition than abundance. A snorkeler often sees the same fish twice and counts it as 2 different species, because males and females look nothing alike.

Seasonality

Location

Rock wrasse live in the eastern Pacific from Point Conception in Santa Barbara County south to Guadalupe Island off north-central Baja California and into the Gulf of California. A few records reach as far north as the Monterey breakwater on the central California coast, but the population is centered south of Point Conception. They belong to the rocky reef biome and the kelp forest biome, and they hold on structure that has both hard bottom and open sand next to it. The sand is not incidental. Rock wrasse spend the night buried in it. They also dart for it when startled during the day. The reefs they prefer are the ones with clean sand patches at the base. Most snorkeling encounters happen from the surface down to about 30 feet, in warm summer water when visibility on the mainland reefs is good. The species has been recorded as deep as 259 feet, but the fish a diver or snorkeler actually meets are shallow.

A rock wrasse feeds by day and stops feeding when the sun starts to go down. About 20 minutes before sunset, it swims to a patch of sand next to its reef and buries itself completely except for the top of its head. About 20 minutes before sunrise, it reappears. Very low overnight tides sometimes leave a buried fish stranded in a wet pocket of sand in the early morning, which is one of the ways beach walkers occasionally find them out of water.

Deep Dive

The single most useful thing to know about the rock wrasse is that a snorkeler who does not know its life history will think they have seen 2 or 3 different species on the same reef. Many rock wrasse hatch as females and later change into males, but not all of them take that path. Histological work at Santa Catalina Island found that only about 38% of the males studied there had once been female, and the rest grew up as males from the start. Biologists call this pattern protogyny, which is the name for a sex change that goes only from female to male. The change begins in larger fish and involves both a rebuild of the reproductive organs and a change in color and marking. The result is 3 visually distinct life stages on the same reef.

A juvenile rock wrasse is bright green, with a thin white stripe running the length of its side and a single black eyespot in the middle of the dorsal fin. Older females fade to pale green or a dull brownish yellow, scattered with small black dots across the upper back. Their eyes are bright red. There is no bar on their side. The largest fish, once they have finished transitioning to males, keep the base color but add a diagnostic marking: a broad black bar edged in pale white or blue, set just behind the pectoral fin. Their pectoral fins take on a yellow cast. The bar is what makes males identifiable at a glance underwater. A pale green or brownish yellow fish with no bar is a female or a fish that has not yet changed. The same fish with the black bar behind its pectoral fin is a male. Both belong to the same species, and many of the males on the reef spent years as females before they were males.

The rock wrasse is a member of the wrasse family, the same family as the California sheephead. Sheephead is the larger, better-known relative on the same reef, and both species share the sex-change pattern, though a sheephead is far larger, transitions later, and looks nothing like a rock wrasse. Rock wrasse reach a maximum of 15 inches and a maximum reported age of 14 years, and a fish over 12 inches is uncommon. The body is long and pencil shaped, with a small mouth that carries surprisingly prominent teeth. In the front of both jaws sit 2 pairs of enlarged canines, plus another large canine at the rear of the upper jaw.

Those teeth match the diet. Rock wrasse feed almost entirely on hard-shelled prey: snails and other gastropods, small crabs, shrimp, amphipods (small shrimp-like crustaceans that live in sand and kelp), clams, scallops, mussels, and slow-moving spiny-skinned animals like sea stars, sea cucumbers, and small sea urchins. Juveniles and smaller adults have also been documented picking parasites off the skin and gills of other fish, particularly around the Isthmus of Santa Catalina Island. This cleaning behavior is common in tropical wrasses but rare in temperate species, and rock wrasse are one of the few Southern California fish that do it at all. It is not a full-time job for them the way it is for a cleaner wrasse on a Pacific coral reef, and most of a rock wrasse's day is spent hunting shelled prey along the sand and reef edge rather than cleaning other fish.

The mating system was worked out by Michael Adreani and Larry Allen at California State University, Northridge, in a study published in the journal Copeia in 2008. They followed rock wrasse around Big Fisherman Cove on Santa Catalina Island for 18 months and found that the species uses 2 different spawning strategies at once, sorted by size. Fish smaller than about 8 inches spawn in groups. Aggregations of 8 to 12 fish dash up into the water column and release eggs and sperm into the current at the same moment. Larger males, the ones with the black bar, defend small territories on the reef of about 43 to 54 square feet. Inside those territories, a large male tries to pair with a single female at a time, with an elaborate courtship display beforehand: vertical rushes at the female and side-on lateral turns that show off the black bar. Actual pair spawns were rare in the study. The researchers witnessed only 3 across the whole 18 months, though the territorial defense went on all day. Group spawning made up almost all of the reproduction. Spawning peaks in July and August, and it happens in the morning. The fertilized eggs drift with the current as plankton, and there is no parental care.

Documented predators of rock wrasse include kelp bass, other larger reef fish, and shorebirds that take juveniles when they can catch them. The number of predator studies for this species is small, and the full list is almost certainly longer than what is on paper. The 2 best-documented behaviors both point to danger at night and from below. A rock wrasse startled during the day dives into sand rather than fleeing into open water, and every rock wrasse ends its day buried in sand with only its head exposed. Both behaviors are widely read as defenses against predators, particularly at night.

Rock wrasse are not fished commercially and are not spearfished. They are caught by pier anglers on light tackle with mussel or worm baits, most often at the piers around Avalon on Catalina Island. Under California ocean sport fishing regulations they fall under the general finfish limit, with no size or season restriction. For a snorkeler, the fishery matters less than the biology. The small pale fish drifting through the kelp and the larger fish with the black bar cruising the same reef are the same animal at 2 different points in its life. Both of them once looked like a bright green juvenile with a spot on its back.