The rock bass is one of the most common fishes native to many North American regions, all the way from the Great Lakes system to the Nieces River in Texas.
One was caught in York River, Ontario, Canada, in 1974, and the second record was set at Lake Erie, Pennsylvania, USA, in 1998.
The red-eyed genus is so common that you’d think it’d be quite easy to reel in a monstrous rock bass.
However, this is not the case, and they hardly grow beyond a certain limit. Stay put as we discuss more about the Rock bass, including its distribution, common features, diet, and mating behavior.
Table of Contents
Physical Description
The rock bass belongs to the genus Ambloplites, which means blunt shield. The species name, rupestris, refers to their behavior of living in rocky water bodies.
Spines
Like other sunfish, rock bass have an average of six spines on their anal fin and at least nine soft anal rays.
The larger dorsal fins also have at least 10 spines and a maximum of 13 soft dorsal rays.
Spotted
Another unique rock bass feature is dark spots on its body. The spots appear in rows next to the lateral line and then go further down the ventral side.
Color
Rock bass are especially popular for their red eyes. The rock bass has yellowish-brown fins, while the gill plates have a black spot on the tips.
Their bodies are a blend of different colors, starting with a dark brownish to greenish, transferring to a lighter green, then fading to yellow or whitish-green towards their ventral side.
Size
Rock bass is relatively small in size, averaging between 20 and 25 cm. Don’t be fooled by the IGFA records because they rarely weigh 3 pounds.
The rock bass is also called “red eyes” due to their bright, red eyes.
Geographic Distribution
Ambloplites rupestris is one of the common fishes found throughout North America. In the United States, they are native to:
North Atlantic region
St. Lawrence
Great Lakes
Hudson Bay
River drainages
Northern to southern Georgia
Northern Alabama
Missouri.
Rock bass also does well in regions of the east-central of the US. Although native to the above regions, the United Fish Commission introduced the fish between 1889 and 1936 in the following regions:
New Hampshire
Southwards towards North Carolina and Virginia’s River Roanoke
The western states, including Wyoming, California, Washington, and Colorado
Rock bass were even transferred to as far as Europe, especially France and England, in the 1800s.
Habitat
The Rock bass is primarily a freshwater fish, preferring aquatic biomes such as ponds, streams, and lakes.
Since they don’t have any special means of fighting off predators, they love heavily vegetated areas for hiding.
That’s why they stay in areas with aquatic forests and rocks.
The fish also do well in areas with temperatures ranging between 10 and 28 degrees Celsius.
These regions often have clear water as opposed to the murky areas so that the fish can spot predators and hide in time.
Their preference for sandy or rocky habitats earned them the name rock bass.
When these fish were introduced to Europe, they found slightly different habitats from their American counterparts.
Ecologists have discovered that they have adapted to the alien habitats, although they prefer something close to the North American habitat and avoid areas with fast-moving waters.
The ponds, streams, or lakes should be at least 2.94 ft (1.2m) deep.
Reproduction
By about 2 to 3 years of age, rock bass have attained sexual maturity and can now look for mates when the season comes.
The mating season extends from early summer to spring when temperatures are between 13 and 15 degrees.
Like the smallmouth bass, the spawning occurs in shallow waters.
Being polygynandrous, both male and female rock bass have different mates all through the breeding season.
Male rock bass create a nest for spawning using their tails to get rid of debris. The result is a circular depression 20 to 30 cm deep, which resembles a bowl.
Unlike other fish, male rock bass doesn’t have a courtship display, and therefore the creation of a nest is taken as an invitation to mate.
Females and males enter the newly made nest simultaneously as the female produces the eggs and the male sprays gametes.
Depending on the female’s size, they will lay approximately 500 to 5,000 eggs.
After fertilization, the male shoulders the responsibility of guarding the nest until the eggs hatch.
The males will turn dark during this period and move in cycles around the nest to provide security.
3 to 4 days after fertilization, the eggs will hatch, and the hatchlings will be strong enough to leave the nest by 9 to 10 days.
However, only around 70% of rock bass nests are successful due to predators.
You don’t want to meet a male rock bass during the spawning season because they are very aggressive.
This fish species move in schools during winter but begin to separate as spring approaches to find mates.
When the nest feels threatened, they rush towards the intruder with their mouths wide open or spread their operculum.
Development
The eggs hatch several days after fertilization to produce rock bass larvae, often around 5.5mm.
Fish larvae lack melanophores which are connective tissue cells that produce melanin. Melanophores in rock bass larvae begin to form at about 6.8mm.
The larvae should develop pectoral, caudal, anal, and dorsal fins at around 8.6mm in size. The pelvic fin appears last at 13.5mm.
The hatchlings are expected to attain a length of 5cm in one year, which should double by the second year and finally reach a length of 16cm at age 3.
Breeding Interval
Rock bass love mating during spring when temperatures are about 14 degrees Celsius. However, there’s a partial mating season during early summer.
Parental Care
Both males and females are involved in taking care of their young. The females will guard the eggs as long as they are not fertilized then migrate to find a new mate after fertilization.
Male rock bass will take over the nest after fertilization until hatching and look after the spawns until they become independent.
What is the average lifespan of the rock bass?
According to the Max Planck Institute for Demographic Research, rock bass have an average lifespan of 12 years, depending on several factors.
Red eyes only get 5 to 8 years in the wild depending on factors such as the environment, food supply, and level of predation.
Interestingly, they live longer in captivity, with the oldest recorded clocking a whopping 18 years.
How do rock bass communicate?
Like other fish, Rock bass use chemical signals to communicate or perceive whatever is happening in their environment.
Chemoreception is important for identifying other species, locating prey, differentiating between sexes, and escaping predation.
Additionally, they can differentiate between their young, identify their bearing in comparison to their habitats, and signal for migration.
Apart from chemoreception, rock bass use their sense of touch through their giant bass-like mouths.
Rock bass can perceive sight using their big eyes, which earned them a nickname “goggle eyes.”
Diet and Feeding Habits
Rock bass’s main diet comprises aquatic plant species that grow in their habitats. That’s why they prefer highly vegetated habitats.
Insects, small crustaceans, smaller larvae, and fish, including those of similar species, are also on the menu.
Predation
Known rock bass predators include:
Walleyes (Sander vitreus)
Northern pike (Esox iucius)
Humans (Homo sapiens)
Muskies (Esox masquinongy)
Large-mouth bass (Micropterus salmoides)
Adult rock bass also hunt smaller adult and young rock bass. The main anti-predatory adaptation for this fish is camouflaging because their greenish bodies blend well with the vegetative environment.
How do rock bass benefit the environment?
Rock bass are predators, meaning they keep the population of certain prey in check. For example, they feed on smaller fish, ocean vegetation, and aquatic crustaceans.
This helps suppress the population of these organisms and keep their population densities at favorable levels.
They also provide food for several predators, which helps maintain ecological balance.
Another rock bass role is that they are hosts in specific ecosystems. Copepods, smaller parasitic crustaceans, and anchor worms depend on the rock bass for survival.
Anchor worms are parasites that attach themselves externally to the rock bass skin and feed. However, they cause skin damage and reduce the average lifespan of the rock bass.
Are rock bass beneficial to humans?
This species is beneficial to humans in the following ways:
Human Food
Quite frankly, despite their huge population, not many people want to eat rock bass. There are more popular species for food out there.
However, rock bass is edible.
Most anglers agree that they make for a good dinner if you know how to prepare them. Their unpopularity stems from their lack of reasonable meat compared to other bass.
For example, smallmouth and large-mouth bass have a big belly that holds a lot of meat.
Fish Sporting
Most bass species, including rock bass, spotted bass, and large-mouth bass, are good fish for sporting due to their vast numbers.
Hundreds of recreational events and competitive tournaments are held each year to hunt this sportfish, meaning there is a multi-million-dollar industry built around rock bass.
Unfortunately, sport fishing and ecotourism, in general, can negatively affect the ecosystem. Killing lots of fish deprives other fish of food, allows the aquatic vegetation to overgrow, and all this creates an ecological imbalance.
Pollution from oil and gas leaks, littering by sportfishing enthusiasts, and even noise pollution from boats negatively affects numerous efforts to maintain healthy and clean ecosystems.
Rock Bass Conservation Status
Earlier on, we mentioned that the fish thrives in numerous environments in North America. They were also introduced to many Europe drainages and seemed to have successfully adapted to their native and alien environments.
Huge rock bass populations mean that they are successfully flourishing and are nowhere near extinction.
In fact, they are categorized by IUCN red list as under “of least concern.” This means they don’t need any conservation management plan or monitoring because their population is stable.
Although they are not something that most people would prefer to eat, they have to be managed to some extent as a sport fish.
You can find some slot limits in different water bodies, meaning you cannot sport fish rock bass of certain lengths.
Additionally, artificial ponds or nurseries are some management tools created to manage rock bass populations.
Lastly, you cannot keep rock bass at home without permission because there are regulations on who can keep this sport fish.
