SoCal’s Bluewater Sharks: The Blue Shark and Shortfin Mako

The first time I saw a blue shark was during the summer of 1975. I am certain of the timing because that time frame was the first time I dived at the Channel Islands. And when we were on our way to and from the islands during daylight hours we were almost certain to see the dorsal fins of dozens of blue sharks knifing their way along the surface. 

That is not the case today. But maybe, just maybe, it can be that way again.

When I started working as a dive instructor at Chuck Nicklin’s San Diego Diving Locker in 1975, I met current-day IMAX filmmaker Howard Hall and a small group of guys who were very interested in diving the open ocean simply to see what was there. I did everything I could to be part of that group. Lucky me, before long I found myself spending a lot of days exploring the open sea as we learned where and how to attract blue sharks and shortfin mako sharks. 

Today, in locations all around the sport diving world there is a wide selection of expeditions targeting various species of sharks. But that was not the case in the mid-1970s. At that time the only known place that provided a good chance of seeing and photographing any species of big shark was in South Australia on tours led by Rodney Fox. The victim of a great white shark bite suffered while spearfishing, Rodney became a champion for sharks and began leading great white shark filming expeditions. 

Rodney’s trips usually produced some good filming opportunities. But they cost roughly $10,000 per person if memory serves me correctly.

The ability to predictably attract blues and makos was big news in the diving and filming communities. In short order Howard and I were constantly writing articles and shooting films, or segments of films, for shows all over the world. And our diving friends were always asking to come along when we were filming sharks.

I don’t recall the exact date but somewhere in the early 1980s, current-day filmmaker and longtime friend, Bob Cranston, and I decided to create a business taking caged divers into the open sea off San Diego to see and photograph blues and makos. Our idea worked. We had plenty of clients and loads of sharks. In fact, one of the problems we often encountered was having too many sharks. 

I realize it might sound like a sea story full of exaggeration, but in those days we were almost always able to attract at least 20 sharks, and there were days we had more than 100. Most were blues, but approximately 10 percent were makos. 

Soon other dive operators began running shark trips and Bob and I sold our business to Paul “Doc” Anes. Doc ran his shark diving expeditions for several years, but like all the operators, after a few years he found it increasingly difficult finding sharks. And when the sharks did show up they were almost always much smaller than the animals we had been seeing a few years earlier. 

What happened, you ask?

The answer is pretty straightforward. The scarcity and smaller size was the direct result of shark populations being decimated by commercial fishing. Longline and drift gillnet fisheries clobbered these highly migratory species even though in many cases the sharks were not the targeted species. The fishermen thought of the sharks, especially the blues, as incidental kill. A nuisance. Within a few years the shark diving operators in southern California were no longer able to run shark trips because they knew there was a significant possibility of getting skunked.

I am not sure exactly when Doc and other operators quit running their shark diving expeditions in California. But I do know that in 1996 while producing a film about sharks for the PBS series Nature, I worked 19 days in the open ocean in southern California trying to attract blue sharks. Sadly, there was not one second during those days that we were able to attract two six-foot long blues at the same time. Fifteen years earlier that would have seemed impossible. 

I am not suggesting that over the last two decades no one has seen or photographed a blue shark or a shortfin mako shark in southern California. That would not be true. But I am saying the sharks were scarce. 

And now for some good news: In May and June of this year I joined two groups of divers who went to sea in hopes of attracting blue sharks and shortfin mako sharks. And we had sharks both days. Not a lot of sharks, but enough that I would like to go again. Furthermore, the trips I went on were not the only ones run by various operators in recent months. And to my knowledge the success rate in attracting the sharks has been good. They are not getting big numbers of sharks. But they are not getting skunked, either.

We can all be encouraged for three reasons. One, people are finding some sharks, both blues and shortfin makos. Two, unlike only a few years ago, if you want to go on a shark diving trip you can probably arrange to do so. Three, there is a subset of the diving community that appreciates sharks enough to pay their money and take their chances. These are the types of divers who often become the energy behind and voices for shark conservation. They — and their dollars — are important to the sharks’ survival. We need these advocates, and they are stepping up. 

Here’s a bit of natural history on blue and shortfin mako sharks, to remind us all why these magnificent creatures are worth protecting.

Adjectives such as sleek, graceful and gorgeous are not the descriptive terms that normally come to mind when discussing sharks. But in the case of the blue shark, Prionace gluaca, these modifiers are spot on. When blues are sighted on sunny days in relatively clear, shallow water the brilliance of their shimmering indigo coloration is nothing short of absolutely stunning. Their slender body, long conical snout, long pointed pectoral fins, moderately sized dorsal fin and asymmetrical tail fin with the upper lobe being noticeably larger than the lower lobe, further characterize blue sharks. 

Blue sharks typically roam between the surface and 500 feet in temperate seas worldwide. However, they are also known to occur in deeper, colder water in tropical regions with occasional surface sightings as well. Blue sharks are highly migratory, a characteristic that makes what might seem like “local populations” highly vulnerable to commercial fisheries around the world. 

The diet of blue sharks consists mainly of a variety of small schooling fishes, pelagic crustaceans and cephalopods. They are opportunistic feeders and are also known to feast upon carcasses of floating marine mammals and trash from boats. 

As is the case with many sharks, loosely organized local populations of blue sharks tend to be sexually segregated. As a rule, in southern California we encounter almost all males in the summer and fall, and almost all females in winter and spring.

The largest documented blue shark measured just short of 13 feet long, but they are said to grow to 20 feet. Males attain sexual maturity at the age of four to five years old at a length of at least six feet. Females generally require another year or so to reach maturity at a length of greater than seven feet. 

As with all sharks, fertilization is internal. After a gestation period of nine to twelve months pups are born live. Litter sizes average 25 to 50 pups. 

The shortfin mako, Isurus oxyrynchus, is a member of the mackerel shark family (Lamnidae), a group that also includes the great white, salmon and porbeagle sharks. Usually referred to as mako sharks or bonito sharks in California, shortfin makos are the sleekest of all the mackerel sharks. But they are solidly built, and a healthy adult is a very impressive, muscular looking animal. Having been clocked at over 20 miles per hour, shortfin makos are often said to be the fastest of all the sharks.

While occasionally seen in nearshore areas, shortfin makos typically roam between the surface and 500 feet in tropical and warm temperate oceans around the world. Like blues, shortfin makos are distinctly countershaded, a pattern that helps them blend in with the water colors of their surroundings. The back and upper portion of these sharks is a beautiful indigo blue while the underbelly is whitish. 

Shortfin makos have a torpedo-shaped body, distinctly pointed snout, relatively large black eye, stubby pectoral fins (hence the name shortfin), and a nearly symmetrical tail fin. The tail is reinforced with a sizeable caudal keel. As with most sharks, adult females are the larger sex. They attain a length of 12.5 feet while weighing more than 1,400 pounds.

Shortfin makos have a tendency to swim with their mouth open wide enough that it is easy to see a number of long, sharp teeth. Combine that “toothy look” with a muscular, torpedo-shaped body that often carries stringy-looking copepod eggs concentrated around the face and on the dorsal fin, and you have an animal that has the look of a Hollywood sea monster.

The typical diet of shortfin makos includes tunas, anchovies, sea basses, mackerel, cods, and swordfish among other bony fishes, other sharks and squids. Shortfin makos possess long, pointed, spear-like teeth designed for impaling and grasping fast moving fish in the open ocean.

The circulatory system of shortfin makos enables them to maintain a core body temperature that is a few degrees higher than ambient water temperature. Elevated body temperature provides faster muscular response and enables makos to swim fast without consuming too much energy.  

Makos are livebearers, but that is not the complete reproduction story. After internal fertilization the female carries the eggs inside of her body. The young sharks develop inside of the egg and hatch months later while still inside of the mother. To gain further nutrition early hatchers consume unhatched eggs inside of dear ol’ mom in part of a reproductive strategy known as oophagy. 

For a lot of us who’ve been diving for many years, it’s easy to reminisce about “the good ol’ days” when it seemed like our oceans held unlimited abundance. But when we’re done telling sea stories, we can choose to advocate for species that have been hard-hit by overfishing. If divers won’t speak out in support of shark conservation, who will?