DIVE DRY WITH DR. BILL #648: BE NOT AFRAID
I'm always amused when I do a night dive and people ask as I'm gearing up or returning if I'm afraid I'll get eaten by a shark. After more than 50 years of diving not a single one has eyed me the way I stare at a flank steak on my barbie. I've had many different species of sharks in many places around the world, including great whites, swim right past me with obvious indifference, similar to the way I look at asparagus if it is placed on my plate.
During summer one thing that worries me more than sharks are the hordes of snorkelers that frequent Casino Point. Of course these people have good intentions since they all want to pay a visit to Catalina's world beneath the surface. However, many of them don't get properly trained prior to entering and others are on their own and haven't learned proper dive park etiquette (or how to read the posted signs). When I walk down the stairs with 100 pounds of dive gear in addition to my personal tonnage, or try to exit the water after my dive, having snorkelers blocking the lower stairs is not only a violation of dive park rules but a real potential for disaster if I should fall on them. It would be like a Mack truck striking a vintage VW bug (or, worse, an Isetta if you remember those)!
So that's why I generally prefer to dive at night during summer and fall. Now that I've had my little rant, let's get back to the issue of elasmobranchs, the subclass of the cartilaginous (as opposed to bony) fish that includes the sharks and rays. Thankfully Discovery Channel's Shark "Weak" is over and once again I failed to watch a single story. Of course since I don't have TV that was quite easy to accomplish. I avoid "Shark Weak" like I avoid "Keeping Up With the Kardashians" since both are utter nonsense in my opinion. The Discovery Channel promised this year would be different, but I've heard that before and friends tell me nothing had changed this year either. Well, that's rant number two in this column and it's still early! Stay tuned.
This year the sad ecological state of the dive park as well as my continued pondering about the meaning of life following the death of my friend Packy has limited my desire to spend much time in the water. I didn't even do my first night dive this year until Bastille Day. Did I see any sharks? Yes, I did. Two utterly harmless horn sharks that were more afraid of me than I could ever be of them. Of course they ARE the only species of shark that has ever "attacked" me. One year I tried to move a small (18") one to get better video, and it swam up and starting "biting" my wetsuit at chest level. I laughed so hard, the regulator fell out of my mouth.
Horn sharks (Heterodontus francisci) are reported to reach a maximum length of just over three feet, although reports by divers have suggested as much as 4-5 feet. Sounds fishy to me. They are found from San Francisco into the Gulf of California (aka Sea of Cortez) and Dr. Milton Love states that there are reports of them in Ecuador and Peru. Along our coast they are uncommon above southern California, although with the warm water this year they may be found further north.
Horn sharks are named for the sharp spines in front of each dorsal fin that provide some defense against potential predators. These spines are probably the only way a horn shark can hurt a diver.. but only if they are careless and ignorant enough to try to grab one! Their bodies are brown to gray on the back with black spots. There are distinctive ridges above each eye. Rather than giving you a toothy grin if you face off with one, they look more like a puppy dog. Their teeth are adapted more for grinding up prey which consists of crustaceans (shrimp and crab), molluscs (scallops, small abalone, squid and octopus), echinoderms such as purple sea urchins and even small fish. Marine mammals including sea lions and elephant seals are known to eat them and I have encountered partially eaten ones being scavenged by crabs.
During the day horn sharks generally seek the shelter of small caves and nooks in the rocky reef, at least in the shallows. They tend to be very lethargic, not unlike some couch potatoes I know. At night they "spring" into action within an hour or two of sunset.... kind of like some of my vampire relatives in Transylvania. Fortunately the shark's teeth are not adapted to sucking blood like mine! After their nocturnal foraging, they return to their hiding places as daylight approaches.
Shark sex can be pretty brutal if you're a female. Females of the species Homo sapiens may agree. They are sexually mature at about two feet in length. During winter the male grasps his sweetheart's pectoral fin in his mouth and begins copulation which may last more than half an hour. No comment. Apparently she may be able to store the sperm as females lay eggs for several months between January and April. Of course they may also be polyamorous! Eggs are encased in a tough coating that has spiral flanges along its length. Perhaps such a structure would improve the completion percentage of a few NFL quarterbacks I know!
The female apparently grasps the egg in her mouth and wedges it into nooks and crannies where it will be less affected by surge and swell. Dr. Love (I'm Dr. No Love, sniff) indicates there is strong disagreement about how long it takes the egg to develop into a young horn shark. Based on my observation of very young sharks in the 5-6" range during June, I'm going with the 8-10 week estimate rather than the 7-9 month one. Divers occasionally pick up the eggs and "candle" them against the sun to see the yolk or developing youngster. Egg predation occurs occasionally with holes drilled in the tough coat. This could be due to an octopus or a snail known as a Kellet whelk.
So, no... I have little fear of sharks when diving at night. Certainly it is possible that "the landlord" may be cruising nearby since they are seen in our waters. However, the sound of my "heavy breathing" through my regulator and my bright video lights probably drive them away when I submerge. And, as far as the lady-go-divers go, they need not worry in the least... after all, sharks are MAN eaters!
© 2015 Dr. Bill Bushing. For the entire archived set of over 650 "Dive Dry" columns, visut my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Horn shark up close and personal and defensive dorsal fin spine; horn shark egg and baby (about 7")
I'm always amused when I do a night dive and people ask as I'm gearing up or returning if I'm afraid I'll get eaten by a shark. After more than 50 years of diving not a single one has eyed me the way I stare at a flank steak on my barbie. I've had many different species of sharks in many places around the world, including great whites, swim right past me with obvious indifference, similar to the way I look at asparagus if it is placed on my plate.
During summer one thing that worries me more than sharks are the hordes of snorkelers that frequent Casino Point. Of course these people have good intentions since they all want to pay a visit to Catalina's world beneath the surface. However, many of them don't get properly trained prior to entering and others are on their own and haven't learned proper dive park etiquette (or how to read the posted signs). When I walk down the stairs with 100 pounds of dive gear in addition to my personal tonnage, or try to exit the water after my dive, having snorkelers blocking the lower stairs is not only a violation of dive park rules but a real potential for disaster if I should fall on them. It would be like a Mack truck striking a vintage VW bug (or, worse, an Isetta if you remember those)!
So that's why I generally prefer to dive at night during summer and fall. Now that I've had my little rant, let's get back to the issue of elasmobranchs, the subclass of the cartilaginous (as opposed to bony) fish that includes the sharks and rays. Thankfully Discovery Channel's Shark "Weak" is over and once again I failed to watch a single story. Of course since I don't have TV that was quite easy to accomplish. I avoid "Shark Weak" like I avoid "Keeping Up With the Kardashians" since both are utter nonsense in my opinion. The Discovery Channel promised this year would be different, but I've heard that before and friends tell me nothing had changed this year either. Well, that's rant number two in this column and it's still early! Stay tuned.
This year the sad ecological state of the dive park as well as my continued pondering about the meaning of life following the death of my friend Packy has limited my desire to spend much time in the water. I didn't even do my first night dive this year until Bastille Day. Did I see any sharks? Yes, I did. Two utterly harmless horn sharks that were more afraid of me than I could ever be of them. Of course they ARE the only species of shark that has ever "attacked" me. One year I tried to move a small (18") one to get better video, and it swam up and starting "biting" my wetsuit at chest level. I laughed so hard, the regulator fell out of my mouth.
Horn sharks (Heterodontus francisci) are reported to reach a maximum length of just over three feet, although reports by divers have suggested as much as 4-5 feet. Sounds fishy to me. They are found from San Francisco into the Gulf of California (aka Sea of Cortez) and Dr. Milton Love states that there are reports of them in Ecuador and Peru. Along our coast they are uncommon above southern California, although with the warm water this year they may be found further north.
Horn sharks are named for the sharp spines in front of each dorsal fin that provide some defense against potential predators. These spines are probably the only way a horn shark can hurt a diver.. but only if they are careless and ignorant enough to try to grab one! Their bodies are brown to gray on the back with black spots. There are distinctive ridges above each eye. Rather than giving you a toothy grin if you face off with one, they look more like a puppy dog. Their teeth are adapted more for grinding up prey which consists of crustaceans (shrimp and crab), molluscs (scallops, small abalone, squid and octopus), echinoderms such as purple sea urchins and even small fish. Marine mammals including sea lions and elephant seals are known to eat them and I have encountered partially eaten ones being scavenged by crabs.
During the day horn sharks generally seek the shelter of small caves and nooks in the rocky reef, at least in the shallows. They tend to be very lethargic, not unlike some couch potatoes I know. At night they "spring" into action within an hour or two of sunset.... kind of like some of my vampire relatives in Transylvania. Fortunately the shark's teeth are not adapted to sucking blood like mine! After their nocturnal foraging, they return to their hiding places as daylight approaches.
Shark sex can be pretty brutal if you're a female. Females of the species Homo sapiens may agree. They are sexually mature at about two feet in length. During winter the male grasps his sweetheart's pectoral fin in his mouth and begins copulation which may last more than half an hour. No comment. Apparently she may be able to store the sperm as females lay eggs for several months between January and April. Of course they may also be polyamorous! Eggs are encased in a tough coating that has spiral flanges along its length. Perhaps such a structure would improve the completion percentage of a few NFL quarterbacks I know!
The female apparently grasps the egg in her mouth and wedges it into nooks and crannies where it will be less affected by surge and swell. Dr. Love (I'm Dr. No Love, sniff) indicates there is strong disagreement about how long it takes the egg to develop into a young horn shark. Based on my observation of very young sharks in the 5-6" range during June, I'm going with the 8-10 week estimate rather than the 7-9 month one. Divers occasionally pick up the eggs and "candle" them against the sun to see the yolk or developing youngster. Egg predation occurs occasionally with holes drilled in the tough coat. This could be due to an octopus or a snail known as a Kellet whelk.
So, no... I have little fear of sharks when diving at night. Certainly it is possible that "the landlord" may be cruising nearby since they are seen in our waters. However, the sound of my "heavy breathing" through my regulator and my bright video lights probably drive them away when I submerge. And, as far as the lady-go-divers go, they need not worry in the least... after all, sharks are MAN eaters!
© 2015 Dr. Bill Bushing. For the entire archived set of over 650 "Dive Dry" columns, visut my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Horn shark up close and personal and defensive dorsal fin spine; horn shark egg and baby (about 7")
