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Dive Dry with Dr. Bill

#364: Salema... Night and Day

Now Jacques-Yves Cousteau was one of the childhood influences that led me into a life of crime... er, I mean marine biology and SCUBA diving. I was also privileged to work with him and Jean-Michel during the filming of a two hour documentary in the his "Rediscovery of the World" series back in 1985. Of course he stayed on the Calypso and I worked from their experimental windship Alcyone with Jean-Michel many miles away. The experience was certainly the achievement of a dream dating back to when I saw his first documentary, "The Silent World," as a young boy in landlocked Chicago.

After nearly 50 years of SCUBA diving and 45 years of marine biological research, I have to take issue with my icon. Even though I've lost some of my auditory acuity (most likely due to my diving), I still cannot refer to the underwater world as "silent." In fact, it's quite noisy if you pay attention. There are constant snaps, crackles and pops from pistol shrimp and other invertebrates. Anglers are aware of some of the fish families including the croakers and grunts that also make noise... not to mention the clicking of the male garibaldi as it defends its nest. Croakers include the white sea bass and black croaker while the local grunt representatives are the sargo and salema. Today's column will focus on the latter species, known scientifically as Xenistius californiensis.

Nearly two years ago I wrote about the salema, but I've been researching it and the sargo, the other common grunt in our waters, recently for an upcoming DVD I'm producing. I thought I'd flesh out this species by adding some new information and observations from my night diving. Yes, despite vowing not to do another night dive until the invasive Asian kelp Sargassum filicinum dies off in spring, I did re-enter the water after dark last weekend. It merely confirmed my feelings that this alien invader has ruined night diving for me during its peak annual cycle. I'll just have to rob a few banks so I can afford to travel to warm, tropical climates where this kelp is non-existent.

My filming last weekend consisted almost entirely of pointing my camera up at the plankton and nocturnal worms and crustaceans that dart around in the waters when their main predators are sleeping. On several occasions I captured footage of lone salema swimming in my lights. I remembered from my previous column that although salema school during the day, often in fairly large groups, the schools break up after dark (I guess there are no "night school" classes for salema) and individuals disperse to feed. This is yet another example of how fish behavior varies on a 24-hour or diurnal cycle.

Daytime schooling is most likely an adaptation to avoid death by predation. Large groups of fish swimming together make it harder for barracuda, or cormorants, or other predators to select and grab a meal from the smorgasbord. At night the salema can venture away from the schools under cover of darkness which helps mask them from some of their predators. It is at this time they feed on worms and small crustaceans like amphipods and shrimp. They also feed on plankton, occasionally even during the day. Perhaps their characteristic large eyes help them spot these small morsels thanks to a little moonlight (a little romantic music maestro, please... oops, that's mixing "munching" and "mating"). They will also take advantage of lights on piers to assist in taking their prey.

I guess I should touch on the mating habits of the salema, mainly for my voyeuristic readers. Actually, I can't imagine anyone getting too excited about this topic. Female salema are oviparous, producing eggs that are fertilized as they are cast off into the sea during early spring and summer. Here they drift with the plankton, feeding initially on the yolk and later on plankton as larvae. The duration of their drift allows the young salema to settle in new habitats, or add fresh genetic material to existing populations. When they do settle out of the plankton, they may frequent tidepools or school with the young of other species including black croakers and their grunt relatives, the sargo. I can imagine the noise these youngsters make... just like elementary students practicing their new band instruments! Ugh.

Now salema are known from Monterey up north as far south as Peru, but are rare above Pt. Conception. We mostly see them in our temperate waters during the warmer months, and they may be hanging on into late November here due to the relatively toasty water temperatures we're experiencing. After all, the temperature on last weekend's night dive was 63 F... nothing to sneeze at (unless, like me, you are stupid enough to dive in a 3/2mm wetsuit and aggravate an existing cold). By the way, were you aware that the technical term for a sneeze is a sternutation and sneezes in ancient Greece were often considered to be signs from the gods. I just hope it isn't a sign of a bad cold coming on!

© 2009 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM 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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Salema schooling during the day, and out on the town individually at night to feed.

This document maintained by Dr. Bill Bushing.
Material and images © 2009 Star Thrower Educational Multimedia