DIVE DRY WITH DR. BILL #845: SQUID "FACTS"
To assist in the filming of the market squid (Doryteuthis opalescens), I've been doing a fair bit of research on the species and any scientific studies done on them. I've come to the conclusion that despite the fact market squid are the number one fishery in California, we really are unsure about a lot of the factors involved in their life history. We don't even have an accurate way to assess the population status. They are a difficult species to get to know!
For example, many studies state that squid spawn mainly at night. This probably comes from the fact that squid boats fish almost exclusively at night. Having filmed a number of squid runs over the years, I have documented the fact that they spawn both day and night. Other scientists are coming to the same conclusion. Night... and day... you are the one. Can't shut those pheromones down once they start.
Other journal articles state that squid don't eat while they are spawning. Of course I never combine munching and mating myself... wouldn't be prudent. However, during our recent filming the cameraman captured a male squid chowing down on a baitfish. I guess it didn't read the script. After all, it takes energy to perform for weeks on end... but I wouldn't know!
Many marine biologists believe that temperature is the major factor in determining when and where squid spawn. Some say spawning occurs when the thermometer registers 50 to about 55 degrees Fahrenheit. This had me thinking to the days when I used to dive regularly to 180-200 ft. I never hit a minimum temperature below 50° on those dives. However, I have experienced ice cream headaches diving in shallow water (~70 ft)... all the way down to 46° F.
So if temperature is the controlling factor to initiate spawning, why don't the squid get their kicks down at 200 feet instead of 40 to 120 ft where I've filmed them? My assumption is that oxygen is perhaps more important than temperature. Shallower water has more dissolved oxygen in it than deeper water. In part this is due to the transfer of gasses to the ocean from the atmosphere. It may also be due to phytoplankton photosynthesizing and producing oxygen in the shallower waters where they receive enough sunlight. Squid eggs may also be limited to relatively shallow waters due to the surge and currents, which help bathe them in fresh, oxygenated water.
Temperature of course can be an important factor in years where it varies from the norm. For example, El Niño events create much warmer than normal temperatures especially in the shallower depths. Squid usually do not exhibit much spawning during these events. Given their short lifespan (3 to 10 months), this will mean lower population numbers and smaller spawns in succeeding years. The warmer temperatures may prove problematic for several reasons.
First, warmer water means a lower concentration of dissolved oxygen. Second, warmer temperatures may interfere with the development of the eggs. The biochemical processes involved in growth can be affected by abnormally high or low temperatures. Many species have two different temperature ranges... that within which the animal can survive and a narrower range within which reproduction is successful. This is why some southern species may enter our waters and survive, but not be able to reproduce. An example of this is the "California" Moray, which probably should be called the Mexican moray.
I've been studying our marine environments for seven decades now. There is so much to learn. When people ask if I ever get bored after diving so long. I tell them there is often a new species or behavior to discover, or a new scientific study to read. It would take many lifetimes to really understand our complex ecological communities. Sadly, I only have one (and it is coming to a close sooner than I expected). That's why it is important to pass on observations through my writing and video production so what I have learned does not die with me.
© 2020 Dr. Bill Bushing. For the entire archived set of nearly 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Scientist baffled by squid reproduction and hungry mating squid; temperature too warm and oxygen supply for developing eggs.
To assist in the filming of the market squid (Doryteuthis opalescens), I've been doing a fair bit of research on the species and any scientific studies done on them. I've come to the conclusion that despite the fact market squid are the number one fishery in California, we really are unsure about a lot of the factors involved in their life history. We don't even have an accurate way to assess the population status. They are a difficult species to get to know!
For example, many studies state that squid spawn mainly at night. This probably comes from the fact that squid boats fish almost exclusively at night. Having filmed a number of squid runs over the years, I have documented the fact that they spawn both day and night. Other scientists are coming to the same conclusion. Night... and day... you are the one. Can't shut those pheromones down once they start.
Other journal articles state that squid don't eat while they are spawning. Of course I never combine munching and mating myself... wouldn't be prudent. However, during our recent filming the cameraman captured a male squid chowing down on a baitfish. I guess it didn't read the script. After all, it takes energy to perform for weeks on end... but I wouldn't know!
Many marine biologists believe that temperature is the major factor in determining when and where squid spawn. Some say spawning occurs when the thermometer registers 50 to about 55 degrees Fahrenheit. This had me thinking to the days when I used to dive regularly to 180-200 ft. I never hit a minimum temperature below 50° on those dives. However, I have experienced ice cream headaches diving in shallow water (~70 ft)... all the way down to 46° F.
So if temperature is the controlling factor to initiate spawning, why don't the squid get their kicks down at 200 feet instead of 40 to 120 ft where I've filmed them? My assumption is that oxygen is perhaps more important than temperature. Shallower water has more dissolved oxygen in it than deeper water. In part this is due to the transfer of gasses to the ocean from the atmosphere. It may also be due to phytoplankton photosynthesizing and producing oxygen in the shallower waters where they receive enough sunlight. Squid eggs may also be limited to relatively shallow waters due to the surge and currents, which help bathe them in fresh, oxygenated water.
Temperature of course can be an important factor in years where it varies from the norm. For example, El Niño events create much warmer than normal temperatures especially in the shallower depths. Squid usually do not exhibit much spawning during these events. Given their short lifespan (3 to 10 months), this will mean lower population numbers and smaller spawns in succeeding years. The warmer temperatures may prove problematic for several reasons.
First, warmer water means a lower concentration of dissolved oxygen. Second, warmer temperatures may interfere with the development of the eggs. The biochemical processes involved in growth can be affected by abnormally high or low temperatures. Many species have two different temperature ranges... that within which the animal can survive and a narrower range within which reproduction is successful. This is why some southern species may enter our waters and survive, but not be able to reproduce. An example of this is the "California" Moray, which probably should be called the Mexican moray.
I've been studying our marine environments for seven decades now. There is so much to learn. When people ask if I ever get bored after diving so long. I tell them there is often a new species or behavior to discover, or a new scientific study to read. It would take many lifetimes to really understand our complex ecological communities. Sadly, I only have one (and it is coming to a close sooner than I expected). That's why it is important to pass on observations through my writing and video production so what I have learned does not die with me.
© 2020 Dr. Bill Bushing. For the entire archived set of nearly 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Scientist baffled by squid reproduction and hungry mating squid; temperature too warm and oxygen supply for developing eggs.
