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Dive Dry with Dr. Bill

#439: The Spotfin Croaker

People occasionally ask me why I continue to dive after almost 50 years on SCUBA. Haven't I seen it all, at least here in Catalina's waters? My response is that often enough I see a new species, a new behavior or gain a new insight into the ecological workings of our giant kelp forests. I guess I'm just a slow learner... and not easily bored. I'm currently working on an episode for my "Munching & Mating in the Macrocystis:" cable TV show on the croaker family of fish. Many of you know one of its members, the white sea bass, intimately. There are other relatives of this tasty species seen in our waters as well. As a kelp forest ecologist I generally prefer rocky reef habitats, and these fish often frequent sandy bottoms. Occasionally they'll wander into my neck of the woods... er, kelp forests... and I'll film them.

The family Sciaenidae actually includes both croakers and drums. You might be able to guess (correctly) that these can be noisy fishies. Divers with better auditory acuity than myself can actually hear white sea bass croaking away. Their swim bladders consist of several compartments and are used as a resonating chamber to amplify the sound. I can barely hear a jackhammer, the result of diving for such a long time. While diving in the tropics, I have encountered relatives such as the spotted drum and jackknife... but couldn't hear them either. Of course when I finally get married, this could be of great benefit!

One such species is the spotfin croaker (Roncador stearnsi). This fish frequents soft bottoms from the intertidal to about 60 ft from Pt. Conception down to southern Baja. They are rarer north of Los Angeles, so Catalina is at the northernmost part of their preferred geographic range. This could change as ocean temperatures increase in the coming decades. Dr. Milton Love believes they migrate south in the winter and return to our waters in summer. Some sources indicate they are found in the Gulf of California (Sea of Cortez) and down the mainland coast of Mexico to Mazatlan. Spotfin croaker usually aggregate in small groups of fewer than 50, but on occasion large schools containing hundreds of them may be observed as was the case when I saw them in the dive park.

These fish get their name from the obvious spot at the base of their pectoral fins. Their bodies are bluish-gray on the dorsal surface, brassy on the sides and white on their bellies. They may also have dark, wavy lines along their flanks. According to one source, the largest fish taken weighed 10 1/2 pounds, was about 27" and estimated to be 15 years old. However, the CDF&G website references one of that size weighing 14 pounds. The upper profile of the head a steep, and the mouth is subterminal (beneath the head rather than in front) making it easier to grab food from the bottom.

These fish forage along the soft substrate, feeding mostly on small crustaceans, worms and clams (sometimes just the tips of their siphons for the young 'uns). They use their pharyngeal "teeth" inside the throat to crush these critters and extract the goodies... kind of like using a lobster cracker to break through the hard exoskeleton and extract the meat from the claws... if you're devouring a Maine lobster like I used to do as a kid! No, they weren't native to Chicago... Mom and Dad imported them from New England on special occasions.

Most males are believed to mature at two years and about 9" while the females wait for another year when they are over a foot in length. Males turn more brassy and develop golden pelvic and pectoral fins at this time, and are sometimes referred to as golden croakers. Some ladies like diamonds, others prefer gold (mine had better like SCUBA gear). Spawning happens during the summer months, generally June to September. It is believed to occur offshore. The large schools occasionally observed may be associated with this activity. The young-of-year, about 1 inch long, settle into the surf zone during fall.

Spotfin croaker are a popular recreational sportfish and are taken from shore, piers and small vessels. It has been illegal to catch them commercially since way back in 1915. More than a century ago these fish were extremely abundant. Mission Bay in San Diego was famed for its spotfin croaker fishing, but human activity including dredging and boat traffic diminished their numbers there. San Onofre and Newport Bay were also reportedly good locations to catch them. Fishing is best in the late summer. During the period from 1980 to 1998 landings fluctuated a great deal, ranging from 1,000 to 46,000 fish and averaging almost 15,000 per year. Given my angling skills, I didn't contribute a single fish during that entire time!

© 2011 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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School of spotfin croaker encountered in the Casino Point Dive Park on Catalina

This document maintained by Dr. Bill Bushing.
Material and images © 2011 Star Thrower Educational Multimedia