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Exploring the beautiful nature of California


Marine Fish: Ocean Sunfish


Fishes are aquatic vertebrates that have fins, gills and scales. Gills are the part of the respiratory system that provide surface area for exchanging oxygen and carbon dioxide under water.

Fish are ectotherms, commonly referred to as 'cold-blooded', meaning their temperature is regulated by the temperature of their environment. They have a range of diets, being herbivores, carnivores, or omnivores. Some fish reproduce by laying eggs, while others reproduce by bearing live young.

California fish species reside in freshwater and coastal/marine waters. Coastal, or marine fish are an abundant and valuable resource. However, the ocean's supply is not limitless, and therefore careful planning and education must be undertaken to ensure the sustainability of the world's largest food source.
Ocean sunfish can get as large as 2,000 pounds  The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish in the world. It has an average adult weight of a little over a ton! The species is native to tropical and temperate waters around the globe. Ocean Sunfish resemble a fish head with a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long when their dorsal and ventral fins are extended.

Sunfish live on a diet that consists mainly of jellyfish, but because this diet is nutritionally poor, they consume large amounts in order to develop and maintain their great bulk. Adult sunfish are vulnerable to few natural predators, but sea lions, orcas and sharks will consume them.

Among humans, sunfish are considered a delicacy in some parts of the world, including Japan, the Korean peninsula and Taiwan. Sunfish are frequently, though accidentally, caught in gillnets, and are also vulnerable to harm or death from encounters with floating trash, such as plastic bags.
Females of the species can produce more eggs than any other known vertebrate. Sunfish fry resemble miniature pufferfish, with large pectoral fins, a tail fin and body spines uncharacteristic of adult sunfish.

Ocean sunfish, or molas, look like the invention of a mad scientist. Huge and flat, these silvery-gray fish have tiny mouths and big eyes that vanish into an even bigger body with a truncated tail. Inside a mola’s tiny mouth are two pairs of hard teeth plates shaped with a slightly curved ridge that look kind of like a bird’s beak. Molas eat mainly jellies, from big moon jellies to tiny comb jellies.

To break their dinner into manageable pieces they don’t chew; they suck the jellies in and out of their mouths until they’re reduced to gelatinous chunks. We think that molas can enjoy this potentially painful diet because of a mucus-like lining in the digestive tract that keeps them from getting stung. Molas also sometimes eat squid, fish, crustaceans, sponges, brittle stars, and odd seafloor creatures called crinoids.
Ocean sunfish can be found along the coast of California waters  Molas are slow and deliberate swimmers. Adult molas lack a gas-filled swim bladder, the organ that gives most bony fish exquisite control over buoyancy. Scientists impressed by their slow-motion swimming at first guessed that molas must drift wherever ocean currents take them. But molas in Southern California have been tracked swimming 26 km in a day, at a top speed of 3.2 km per hour—which, to give them credit, is not far off the speed of a yellowfin tuna when it’s just out cruising.

With their tank-like bodies, molas were clearly not built for life in the fast lane, but they hold their own against faster and flashier fishes and are able to live in almost all of the world's oceans. They are known to spend time near the ocean surface but tagging shows that molas are also prolific divers and migrate long distances at depth.

Because molas spend so much time drifting near the ocean surface, they are vulnerable to fishing boats that use drift gillnets. In California, nearly 30 percent of the catch in a swordfish boat can be molas caught by mistake—rivaling or exceeding the number of swordfish caught.
 
 
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