DIVE DRY WITH DR. BILL #770: NOT WARM ENOUGH YET!
Having lost over 40 pounds in my battle with cancer, one of my concerns about returning to the ocean is the lack of "bioprene" (aka natural insulation) to keep me warm. Now, I'm no "warm water wussy" and have (barely) tolerated water temperatures as low as 46° F in my "holy" wetsuit. However, I don't want to get "the shimmy, shimmy shakes" next time I descend into Neptune's realm. Wouldn't be prudent for my videography.
Evidence appears to show fairly clearly that ocean temperatures are warming along the coast of California. The increased frequency of El Niños and other warm water events like The Blobs, and the gradual increase in average ocean temperatures are physical data that illustrate this. It is also reflected by changes in the critters we see in our waters.
Way back in 1931-1933 a Stanford student, Willis Hewatt, did a study of the intertidal critters at Pacific Grove near Monterey. 60+ years later (from 1993-94) another Stanford researcher, Rafe Sagarin, studied the same intertidal region. Sagarin found that eight of nine southern species had increased in number while five northern species had declined. During this period the average local water temperature there had increased 1.3° F and by nearly 4° F during summer.
Having attended Harvard back in the 1960s when Dr. Roger Revelle was teaching there, I was well aware of global warming as was my classmate Al Gore. However, I didn't have the forethought to establish a similar study area here on Catalina when I arrived back in 1969. It certainly would have been interesting to see the changes in marine invertebrates since the island exists in a transitional zone where such effects should be easily observed.
However, changes in fish species composition in our waters have certainly been detected over that period of time. I have been witness to several of these and even identified three species in the Casino Dive Park that were new to our area. I knew them from my diving in the Sea of Cortez a decade ago. All are warmer water species that were mostly unknown from north of Guadalupe Island off Baja until recently. These are the whitetail damsel or gregory (Stegastes leucorus) identified in 2012, the largemouth blenny (Labrosomus xanti) noted in 2016 and the Panamic fanged blenny (Ophioblennius steindachneri) I identified just last year.
Since the damsel was first observed as a youngster, it is most likely it dispersed here as a larval form. It must have survived for several years in the park as I filmed a solitary young adult a few years later. Without a mate, its chance of establishment here was slim to none. The two blennies were both observed as adults and the largemouth blennies included both males and females. Due to the numbers observed, they may have been transported here in a large stream of larvae as swimming up from Baja as a group seems highly unlikely!
These recent introductions are not the only fish crossing from south of the border. When I first came to the island, the northern scythemarked butterflyfish (Prognathodes falcifer) was already known to be in local waters. Although this species is often referred to as tropical or subtropical, it actually tolerates cooler waters pretty well. Down in Mexico it may be found at depths down to a reported 270 m (885 ft). Its ability to survive in the deeper waters allows it to adapt fairly easily to our waters, albeit generally preferring depths closer to the surface.
Another southern species known to be in island waters way back when is the finescale triggerfish (Balistes polylepis), or cochi in Spanish. I have filmed this species in fairly shallow waters in the Sea of Cortez but was surprised to find in my research that it may occupy depths to 1,700 ft off Mexico. That makes it another species which probably had an easy time adapting to SoCal.
For a southern species to adapt to life in our more temperate seas requires several things. First, the water temperature throughout the year should be within the survival range for the species. No self-respecting fish wants to freeze its fins off! It must also find adequate food sources in the new habitat. Some critters are highly selective in what they will eat, and are more likely to starve in a new environment. Fortunately when I moved to California from Chicago, I readily adapted to artichokes, avocados and tri-tip! Those critters which are generalists and tolerate a broader menu are more likely to find something palatable on the local menu.
Now survival is one step in adapting to a new location! However, for the species itself to survive there, and thus expand its geographical range, there is another critical factor. Water temperatures must be in the proper range to induce mating and support the development of the eggs and larvae. This is often a critical factor for any species arriving here. Now I don't have a specific reproductive temperature range as long as a warm blanket is near by. Fish are different.
There is evidence that both the scythemarked butterflyfish and finescale triggerfish are reproducing in our waters. They've both been here for decades. I have filmed small juveniles of the butterflyfish and other divers have noted what appear to be young triggerfish. Another explanation could be that larvae of both species get periodically dispersed to our waters by warm water events, but my money (what little is left) is on reproduction!
I'm getting on in years and probably don't have many years left due to the cancer. That is probably fortunate since I'm really trained as a temperate water kelp forest ecologist. Much as I love diving in warm water, I think it would be difficult to teach this old dog new tricks so I could become a coral reef ecologist. Of course the rate of temperature increase suggests that would be some time in the future!
© 2018 Dr. Bill Bushing. For the entire archived set of nearly 775 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: A juvenile scythe butterflyfish, adult finescale triggerfish (top), baby and adult whitetail damsel (middle), largemouth and Panamic fanged blennies (bottom).
Having lost over 40 pounds in my battle with cancer, one of my concerns about returning to the ocean is the lack of "bioprene" (aka natural insulation) to keep me warm. Now, I'm no "warm water wussy" and have (barely) tolerated water temperatures as low as 46° F in my "holy" wetsuit. However, I don't want to get "the shimmy, shimmy shakes" next time I descend into Neptune's realm. Wouldn't be prudent for my videography.
Evidence appears to show fairly clearly that ocean temperatures are warming along the coast of California. The increased frequency of El Niños and other warm water events like The Blobs, and the gradual increase in average ocean temperatures are physical data that illustrate this. It is also reflected by changes in the critters we see in our waters.
Way back in 1931-1933 a Stanford student, Willis Hewatt, did a study of the intertidal critters at Pacific Grove near Monterey. 60+ years later (from 1993-94) another Stanford researcher, Rafe Sagarin, studied the same intertidal region. Sagarin found that eight of nine southern species had increased in number while five northern species had declined. During this period the average local water temperature there had increased 1.3° F and by nearly 4° F during summer.
Having attended Harvard back in the 1960s when Dr. Roger Revelle was teaching there, I was well aware of global warming as was my classmate Al Gore. However, I didn't have the forethought to establish a similar study area here on Catalina when I arrived back in 1969. It certainly would have been interesting to see the changes in marine invertebrates since the island exists in a transitional zone where such effects should be easily observed.
However, changes in fish species composition in our waters have certainly been detected over that period of time. I have been witness to several of these and even identified three species in the Casino Dive Park that were new to our area. I knew them from my diving in the Sea of Cortez a decade ago. All are warmer water species that were mostly unknown from north of Guadalupe Island off Baja until recently. These are the whitetail damsel or gregory (Stegastes leucorus) identified in 2012, the largemouth blenny (Labrosomus xanti) noted in 2016 and the Panamic fanged blenny (Ophioblennius steindachneri) I identified just last year.
Since the damsel was first observed as a youngster, it is most likely it dispersed here as a larval form. It must have survived for several years in the park as I filmed a solitary young adult a few years later. Without a mate, its chance of establishment here was slim to none. The two blennies were both observed as adults and the largemouth blennies included both males and females. Due to the numbers observed, they may have been transported here in a large stream of larvae as swimming up from Baja as a group seems highly unlikely!
These recent introductions are not the only fish crossing from south of the border. When I first came to the island, the northern scythemarked butterflyfish (Prognathodes falcifer) was already known to be in local waters. Although this species is often referred to as tropical or subtropical, it actually tolerates cooler waters pretty well. Down in Mexico it may be found at depths down to a reported 270 m (885 ft). Its ability to survive in the deeper waters allows it to adapt fairly easily to our waters, albeit generally preferring depths closer to the surface.
Another southern species known to be in island waters way back when is the finescale triggerfish (Balistes polylepis), or cochi in Spanish. I have filmed this species in fairly shallow waters in the Sea of Cortez but was surprised to find in my research that it may occupy depths to 1,700 ft off Mexico. That makes it another species which probably had an easy time adapting to SoCal.
For a southern species to adapt to life in our more temperate seas requires several things. First, the water temperature throughout the year should be within the survival range for the species. No self-respecting fish wants to freeze its fins off! It must also find adequate food sources in the new habitat. Some critters are highly selective in what they will eat, and are more likely to starve in a new environment. Fortunately when I moved to California from Chicago, I readily adapted to artichokes, avocados and tri-tip! Those critters which are generalists and tolerate a broader menu are more likely to find something palatable on the local menu.
Now survival is one step in adapting to a new location! However, for the species itself to survive there, and thus expand its geographical range, there is another critical factor. Water temperatures must be in the proper range to induce mating and support the development of the eggs and larvae. This is often a critical factor for any species arriving here. Now I don't have a specific reproductive temperature range as long as a warm blanket is near by. Fish are different.
There is evidence that both the scythemarked butterflyfish and finescale triggerfish are reproducing in our waters. They've both been here for decades. I have filmed small juveniles of the butterflyfish and other divers have noted what appear to be young triggerfish. Another explanation could be that larvae of both species get periodically dispersed to our waters by warm water events, but my money (what little is left) is on reproduction!
I'm getting on in years and probably don't have many years left due to the cancer. That is probably fortunate since I'm really trained as a temperate water kelp forest ecologist. Much as I love diving in warm water, I think it would be difficult to teach this old dog new tricks so I could become a coral reef ecologist. Of course the rate of temperature increase suggests that would be some time in the future!
© 2018 Dr. Bill Bushing. For the entire archived set of nearly 775 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: A juvenile scythe butterflyfish, adult finescale triggerfish (top), baby and adult whitetail damsel (middle), largemouth and Panamic fanged blennies (bottom).
