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DIVE DRY WITH DR. BILL #832: KEEP YOUR FINGER OFF THE TRIGGER!

Discussion in 'California' started by drbill, Oct 11, 2019.

  1. drbill

    drbill The Lorax for the Kelp Forest Scuba Legend

    # of Dives: 2,500 - 4,999
    Location: Santa Catalina Island, CA
    22,506
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    DIVE DRY WITH DR. BILL #832: KEEP YOUR FINGER OFF THE TRIGGER!

    This has been an amazing summer. I've done 40 dives already (starting in mid August) and will undoubtedly meet my goal of 50 for the year. In fact, I'll probably revise that number upward. The last three summers I've barely gotten any diving in due to my medical condition, but I feel so much better now. Go figure!

    Most of my dives this summer and fall have focused on two things, staring wreckfish (aka GSBs or Stereolepis gigas) in the eye as we both hover around the thermocline, or weeding out the terribly invasive Asian seaweed Sargassum horneri (or as I coined it, "devil weed"). However, there have been some unusual sightings in the dive park recently.

    Although finescale triggerfish (Balistes polylepis) and scythe butterflyfish (Prognathodes falcifer) have been in Catalina waters from my earliest years on the island, I can't recall a single observation of them in the dive park itself. They are said to have arrived during the 1982-84 El Niño but may have reached Catalina during an earlier one in the late 1970s. Both have been seen recently by divers here (along with a few green turtles, Chelonia mydas). Of course I have not seen any of these on my dives in the park, but have encountered them at dive sites elsewhere around the island.

    Finescale triggers tend to be pretty skittish in our waters although they were much more approachable when I dove in the Sea of Cortez. I've never been able to film them here... until now! Jason Manix called me one day and said he had found a dead specimen floating out by one of the docks and he kindly got it and froze it for me. I thought I'd better take a day off from diving and film it before my refrigerator started smelling like a fish market!

    Finescale triggers have a laterally compressed body that is brownish to tan in color with a touch of blue in mature individuals. The eyes are fairly small indicating they are probably daytime feeders. The mouth projects forward and has eight sharp teeth. Maximum length is nearly a yard and they may weigh up to 16 pounds. However the ones we see here tend to be smaller than the ones in Mexican waters. The anal and second dorsal fins are long and when they swim they create an unusual propulsion pattern. They also have a dorsal spine above the eyes that is reported used to wedge themselves into rock crevices at night.

    This species prefers rocky reefs that are adjacent to sandy bottoms (not the kind you find in Coppertone ads though!). It is reported on Mexfish.com that may be found as deep as 1,700 feet... much deeper than I'm willing to venture (but Dr. Sylvia Earle descended to 1,500 ft in a one atmosphere suit). Other sites list their maximum depth at about 200 ft. They are known from as far north as SE Alaska down to central Chile and out to the Hawaiian Islands.

    Their bite can be painful, but fortunately human fingers are not generally on their menu. They prefer sea urchins, crustaceans, worms and molluscs (snails and bivalves). They are said to be good eating and are sold in Mexico. Occasionally anglers fishing from Cabrillo Mole near the Lover's Cove MPA will catch them on hook and line. Striped marlin and sea lions are among their non-human predators.

    Dr. Milton Love states that they are unlikely to live more than seven years. Since they've been seen in our waters for decades, this suggests one of two possibilities. Either they are reproducing here or they are repeatedly been introduced to our waters during warm water episodes (which have been increasing in frequency lately). I have yet to see youngsters here, but given how rarely I actually see them that does not exclude reproduction.

    © 2019 Dr. Bill Bushing. For the entire archived set of over 800 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page

    Image caption: Finescale triggerfish from the harbor and dorsal spine; triggerfish mouth and teeth; finescale triggerfish down south of the border.


    DDDB 832 finescle triggerfish sm.jpg
     

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