DIVE DRY WITH DR. BILL #776: ANCHOVY RUN IN AVALON BAY
The sardine run in South Africa is a spectacular dive from what I am told. Massive schools (or shoals as the Brits would say) of these fish swirl around divers as sharks, billfish and other predators dart in and out of the massive clouds of baitfish. Sadly the closest I got to diving there was at the other end of the African continent, the Egyptian Red Sea.
While I have occasionally seen and filmed schools of Pacific sardine (Sardinops sagax) in our waters, none were even close to the spectacle of that run. Large runs of jack mackerel (Trachurus symmetricus), sometimes mixed with Pacific chub mackerel (Scomber japonicus) can be seen in our waters. These are often accompanied by predators such as yellowtail, barracuda and kelp bass eager to fatten their bellies. Unfortunately sharks are rarely an issue in our waters these days like they were back in the 60s and 70s.
We also get very infrequent runs of northern anchovy (Engraulis mordax) here. However, I don't remember a scene like the one we've been seeing right in Avalon Bay lately. Huge schools of young anchovy have been invading our beaches, totally darkening the shallow waters except from the greenish rings around bathers which are kept at a safe distance by the fish. In the images by Mitch Hammond and Laurel Sanchez, you can see the open water around our swim floats and swimmers. I just returned from Howland's Landing where I went to see my old friend Jean-Michel Cousteau. Anchovy (along with sardines and mackerel) were running up there and down to Two Harbors as well.
Many have asked me why these dense schools of anchovy are present in the bay. I have heard from fishers that the outside waters are also loaded with bait, and the predators with bait as well, making it difficult to tempt those fish into taking an angler's bait. I cannot give a definitive answer to that question without a major grant from an institution. You can't expect us impoverished marine biologists to work for free now, can you?
One possible hypothesis is the very warm water we are currently experiencing. Surface waters in Avalon Bay and the dive park have been 76° F recently and Russ Armstrong recorded 78° F at Cherry Cove. Down at the Scripps Pier in La Jolla it has reached 81° F, the warmest surface temperature there in the history of Scripps. Some have suggested the anchovies migrated further north to escape the hurricanes off Mexico. Another theory is that plankton in our very murky waters could be the draw for the anchovy... munchies galore! Visibility has been so bad recently that I mistook the rock wall at Little Casino Reef for a kelp forest... until I was 15 feet from it!
According to Dr. Milton Love, the northern anchovy has been recorded from the eastern Gulf of Alaska to Cabo San Lucas and into the Sea of Cortez although they are more typically found from southern British Columbia to Magdalena Bay in Baja and in the Sea of Cortez. They tend to be highly migratory, so their presence here may be just a temporary stop on the road to somewhere. Catalina was supposed to be that for me as I planned to teach for a year and head back to Greece... 49 years ago! Schools may be seen anywhere from the surf zone to 300 miles offshore. Schooling tends to be tighter and closer to shore during the day, but during the night they may spread out more.
Northern anchovy may be sexually mature at only three inches and a year in age and all are mature by four years and six inches in length. Therefore the individuals in the water here, if similar in size to the ones I've photographed dead on our beach, may already be reproductive. In California and Baja waters they may spawn year-round. The eggs hatch in just a few days. The species is fairly short-lived with some reaching the ripe old age of seven years.
Like most baitfish, anchovies are planktivores feeding on plant and animal plankton which includes a wide range of different near microscopic critters. Unfortunately that may include diatoms in the scientific genus Pseudo-nitzschia which release the toxic domoic acid. These diatoms bloom along our coast usually in spring and summer. When concentrated by filtering critters such as mussels, clams... or baitfish like anchovies... these can cause death in predators like sea lions and brown pelicans that feed on them. Although concentrations of domoic acid in anchovies may not be lethal, do you want to play with poison? I didn't think so.
© 2018 Dr. Bill Bushing. For the entire archived set of more than 775 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Mitch Hammond's image of anchovies in Avalon Bay taken from Mt. Ada, two images of the fish at the beach by Laurel Sanchez and an enhanced image of a portion of the school I took from the Pleasure Pier; dead anchovies on the beach and the large mouth with underslung lower jaw used to capture plankton and other tender morsels.
The sardine run in South Africa is a spectacular dive from what I am told. Massive schools (or shoals as the Brits would say) of these fish swirl around divers as sharks, billfish and other predators dart in and out of the massive clouds of baitfish. Sadly the closest I got to diving there was at the other end of the African continent, the Egyptian Red Sea.
While I have occasionally seen and filmed schools of Pacific sardine (Sardinops sagax) in our waters, none were even close to the spectacle of that run. Large runs of jack mackerel (Trachurus symmetricus), sometimes mixed with Pacific chub mackerel (Scomber japonicus) can be seen in our waters. These are often accompanied by predators such as yellowtail, barracuda and kelp bass eager to fatten their bellies. Unfortunately sharks are rarely an issue in our waters these days like they were back in the 60s and 70s.
We also get very infrequent runs of northern anchovy (Engraulis mordax) here. However, I don't remember a scene like the one we've been seeing right in Avalon Bay lately. Huge schools of young anchovy have been invading our beaches, totally darkening the shallow waters except from the greenish rings around bathers which are kept at a safe distance by the fish. In the images by Mitch Hammond and Laurel Sanchez, you can see the open water around our swim floats and swimmers. I just returned from Howland's Landing where I went to see my old friend Jean-Michel Cousteau. Anchovy (along with sardines and mackerel) were running up there and down to Two Harbors as well.
Many have asked me why these dense schools of anchovy are present in the bay. I have heard from fishers that the outside waters are also loaded with bait, and the predators with bait as well, making it difficult to tempt those fish into taking an angler's bait. I cannot give a definitive answer to that question without a major grant from an institution. You can't expect us impoverished marine biologists to work for free now, can you?
One possible hypothesis is the very warm water we are currently experiencing. Surface waters in Avalon Bay and the dive park have been 76° F recently and Russ Armstrong recorded 78° F at Cherry Cove. Down at the Scripps Pier in La Jolla it has reached 81° F, the warmest surface temperature there in the history of Scripps. Some have suggested the anchovies migrated further north to escape the hurricanes off Mexico. Another theory is that plankton in our very murky waters could be the draw for the anchovy... munchies galore! Visibility has been so bad recently that I mistook the rock wall at Little Casino Reef for a kelp forest... until I was 15 feet from it!
According to Dr. Milton Love, the northern anchovy has been recorded from the eastern Gulf of Alaska to Cabo San Lucas and into the Sea of Cortez although they are more typically found from southern British Columbia to Magdalena Bay in Baja and in the Sea of Cortez. They tend to be highly migratory, so their presence here may be just a temporary stop on the road to somewhere. Catalina was supposed to be that for me as I planned to teach for a year and head back to Greece... 49 years ago! Schools may be seen anywhere from the surf zone to 300 miles offshore. Schooling tends to be tighter and closer to shore during the day, but during the night they may spread out more.
Northern anchovy may be sexually mature at only three inches and a year in age and all are mature by four years and six inches in length. Therefore the individuals in the water here, if similar in size to the ones I've photographed dead on our beach, may already be reproductive. In California and Baja waters they may spawn year-round. The eggs hatch in just a few days. The species is fairly short-lived with some reaching the ripe old age of seven years.
Like most baitfish, anchovies are planktivores feeding on plant and animal plankton which includes a wide range of different near microscopic critters. Unfortunately that may include diatoms in the scientific genus Pseudo-nitzschia which release the toxic domoic acid. These diatoms bloom along our coast usually in spring and summer. When concentrated by filtering critters such as mussels, clams... or baitfish like anchovies... these can cause death in predators like sea lions and brown pelicans that feed on them. Although concentrations of domoic acid in anchovies may not be lethal, do you want to play with poison? I didn't think so.
© 2018 Dr. Bill Bushing. For the entire archived set of more than 775 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Mitch Hammond's image of anchovies in Avalon Bay taken from Mt. Ada, two images of the fish at the beach by Laurel Sanchez and an enhanced image of a portion of the school I took from the Pleasure Pier; dead anchovies on the beach and the large mouth with underslung lower jaw used to capture plankton and other tender morsels.
