10 Facts about Rockfish, They Aren’t Just Tasty!

2. The longest rockfish ever caught was 121cm (47in)

Rockfish are usually not huge fish, but there are exceptions. Some individuals can grow up to 100cm. The vermillion rockfish, which is a large species, can grow up to 76cm (39in). The longest rockfish ever caught was 121cm (47in)! The world record for heaviest rockfish belongs to a rockfish that weighed 40kg (88lbs). Larger rockfish are usually caught at lower depths, far away from shore.

3. Canary rockfish that are less than 14cm have distinct markings

The average canary rockfish is between 20-23cm. Half of the fish are considered adults when they reach 14cm long. The adults who are smaller than 14cm have long, dark markings along the backside of their dorsal fin. Scientists aren’t sure why smaller canary fish have this adaptation, but it could be helpful to survival. Smaller fish are usually easier prey, but these long black markings might suggest to predators that the fish is poisonous, and should not be eaten.

4. Quillback rockfish have venomous spines along their dorsal fins

Many rockfish species have venomous fins and spines. The quillback rockfish has venomous spines along its dorsal fin. At the base of the spine are venom glands that pump the venom upward. This venom is a defense mechanism that protects the fish from predators. Although rockfish venom isn’t lethal to humans, it causes severe pain, and can lead to an allergic reaction or infection.

5. Rockfish have a swim bladder that allows them to control their buoyancy

Rockfish have closed swim bladders, which are gas filled organs that pull air from the fish’s blood vessels, allowing the fish to keep themselves buoyant. This allows the fish to continue swimming at different depths without using too much energy. This is better for fish that live in deeper waters, because they don’t have to go near the surface to collect air. However, travelling upwards too quickly causes the bladder to expand, and shoot the fish’s stomach out of its mouth.

6. Rockfish usually have bulging eyes, compressed bodies, and large mouths

Since there are over 100 species of rockfish, they all have different sizes, colors, and markings. However, all rockfish share certain physical traits too. For example, rockfish all have bulging eyes and large mouths. They also have protruding jaws that make the fish look like it has an underbite when you look at it from the side.  Rockfish have compressed bodies with spiny dorsal fins.

7. Rockfish eat by swallowing prey whole

Rockfish prey on plankton, larvae, small fish, crustaceans, and sometimes other rockfish. But they do not have particularly strong or sharp teeth for grinding down prey or crushing hard shells. Instead, rockfish feed by inhaling their prey and swallowing it whole. The large mouths and jaws on rockfish make this easy, and bigger species will go for bigger prey. Some rockfish even eat smaller rockfish of different species.

8. During mating, a female pacific rockfish will keep sperm in her body for two months before fertilizing her eggs

Rockfish are viviparous, like humans. This means that eggs are fertilized inside the female, who carries the eggs until they are ready to spawn. However, the pacific rockfish eggs are not fertilized when sperm enters the female. The female pacific rockfish will take sperm in the fall, and store it in her body for two months. Then the female will fertilize the eggs, which hatch inside her and leave her body as larval fish in April or May.

Many rockfish produce over 1,000,000 eggs during mating season

In one mating season, a black rockfish can produce between 125,000 and 1,200,000 eggs. But the canary rockfish has it beat. A single female canary rockfish can have between 260,000 to 1,900,000 eggs during one mating season. However, in both species, not all of these eggs end up fertilized. Females usually absorb some of the eggs back into their bodies.

9. Out of over 100 rockfish species, 32 can be found in the Gulf of Alaska

There are around 109 species of rockfish in the world, and most live in oceans surrounding the United States and Canada. However, nearly one third of these species live in the Gulf of Alaska. Out of 109 species, 32 live in the Gulf. Rockfish generally don’t live in the open ocean or shallow water, and the Gulf of Alaska is rich in deep water corals. Many corals can be found between 150 and 900 meters below the ocean surface.

10. Rockfish can be divided into two groups:  Pelagic and Non-Pelagic

All rockfish can be divided into two groups based on their environments: Pelagic or non-pelagic. Oceanic pelagic rockfish don’t swim close to the ocean floor or surface. They’re not bottom feeders, but you won’t find them in shallow tropical reefs either. Generally, they swim below the ocean’s continental shelf. Non-Pelagic rockfish, however, live near the ocean floor. As their name suggests, they live among rocks and boulders that form habitats.

Pelagic fish are more likely to swim in large schools, while non-pelagic fish are more solitary

Pelagic rockfish swim throughout open waters. Without rocks or reefs to hide around, they are exposed to predators. So these rockfish swim in large schools to stay safe from predators. Hundreds of fish can swim in one school, and different rockfish species have been known to school together. Non-pelagic fish, such as the black rockfish, are more solitary. Their habitats have rocks, boulders, or corals that protect them from predators. They do not need to stay in large groups for protection.

Can you tell the difference?

Although rockfish come in a variety of colors and patterns, some species just look the same. Vermillion, yelloweye, and canary rockfish are often mistaken for one another. Each of these rockfish have yellow to orange scales, but there are a few subtle differences. Below are three pictures of rockfish, one vermillion, one yelloweye, and one canary. Can you tell which is which? Here’s a hint: One species has an obvious difference in its appearance, and its common name gives it away.

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Many rockfish populations have fluctuated over the years. It’s common for a species to be overfished, causing governments to take action to restore the population. Overfishing is the biggest threat to rockfish. Many species are either endangered or threatened.

• Commercial Overfishing
  Overfishing is currently the greatest threat to rockfish. Rockfish have sweet, lean white meat that humans find very tasty. Commercial fishing has had detrimental effects on the black rockfish population in the Chesapeake Bay Region. A 2019 study conducted by the Atlantic States Marine Fisheries Commission found that black rockfish are overfished, causing the population to decline below sustainable levels. The primary prey of black rockfish, menhaden, are also being overfished to create fish oil pills and fish feed.
• Recreational Fishing
  Rockfish are also popular targets for recreational fishers. However, even fishermen who practice catch and release contribute to population decline. In the Chesapeake Bay Region, 9% of black rockfish caught and released alive die because of stress or injuries. Furthermore, when rockfish are suddenly pulled to the surface from low depths, their swim bladder bursts, expelling their stomach and intestines. These fish don’t survive long after release.