Fish eating fish, known as piscivory, is a common occurrence in aquatic ecosystems. As you gaze into a lake or ocean, you may wonder – do fish really eat each other? The quick answer is yes, fish absolutely consume other fish species for sustenance and survival.
In this detailed guide, we’ll explore the fascinating dynamics of piscivory and explain which fish species eat others, why they do it, and what effects it has on aquatic food chains.
From fierce predators like sharks to sly bottomfeeders, most fish are opportunistic feeders that will eat smaller fish when the chance arises. Piscivorous fish play important roles in controlling populations, recycling nutrients, and transferring energy between trophic levels.
However, overfishing of apex predators can cause ecosystems to become unbalanced. Read on as we dive into fish’s piscivorous habits and the complex food web dynamics at play underwater.
Types of Piscivorous Fish
Piscivorous fish species span diverse families and habitats
Piscivorous fish, also known as pisciverous fish, can be found in both freshwater and marine environments across the globe. They belong to a diverse array of fish families and occupy many types of aquatic habitats.
From fierce predators like the barracuda and piranha to opportunistic feeders like the rainbow trout, piscivores use a variety of hunting strategies to catch their prey.
Some of the most common freshwater families that contain piscivorous species include salmonids, esocids (pikes and pickerels), centrarchids (bass and sunfish), and percids (perch). Well-known marine families with pisciverous members consist of serranids (groupers), scombroids (mackerels and tunas), carangids (jacks), and belonids (needlefish).
Piscivores are found everywhere from fast flowing streams to sluggish bays and estuaries. Some occupy shallow vegetated areas while others prefer the open water. This highlights the remarkable diversity of morphological, physiological, and behavioral adaptations that enable different piscivorous fish to thrive.
Common freshwater piscivores
There are many types of freshwater fish that eat other fish. Some of the most common piscivorous fish found in lakes, rivers, and streams include:
- Bass – Largemouth bass and smallmouth bass are ambush predators that use vegetation and structure to surprise prey.
- Pike – Northern pike, muskellunge, and pickerel are stealthy hunters with elongated bodies and razor-sharp teeth.
- Trout – Rainbow trout, brown trout, and brook trout are opportunistic feeders that eat insects, crustaceans, and smaller fish.
- Perch – Yellow perch, walleye, and zander prey on smaller baitfish and juveniles of other species.
- Sunfish – Larger species like black bass, white bass, and rock bass supplement their diets with fish.
The hunting strategies utilized range from lurking motionlessly to pursuing prey over longer distances. Pike and bass rely on burst attacks while trout utilize their strong swimming ability to chase down food. Perch and sunfish use their spiny fins and sharp gill covers to swallow fish whole.
Notable marine piscivores
There are thousands of predatory fish species found in oceans, seas, and other marine environments around the world. Some of the most impressive saltwater piscivores include:
- Sharks – Great white sharks, bull sharks, tiger sharks, and other requiem sharks feed extensively on bony fish and smaller sharks.
- Barracudas – Equipped with razor-sharp teeth, barracudas ambush schools of prey in shallow, warm waters.
- Groupers – Giant groupers, gag groupers, and other genus members lie in wait around structure before inhaling fish whole.
- Tunas – Bluefin tunas, yellowfin tunas, bigeye tunas, and other scombrids chase down fast-moving schools of forage fish.
- Dolphinfish – Also known as mahi-mahi or dorados, these powerful swimmers prey on flying fish, mackerel, and other baitfish near the water’s surface.
Additional examples include snappers like red snapper, jacks like giant trevally, and billfish like marlin and sailfish. Though hunting strategies differ between species, these saltwater piscivores are all superbly adapted at finding and capturing other fish.
Behavioral Adaptations for Piscivory
Physical attributes and features
Fish that specialize in eating other fish tend to have unique adaptations that make them effective predators. Many have elongated bodies and jaws lined with sharp teeth that enable them to swiftly grab and easily swallow their prey.
Piscivorous fish may also have keener vision compared to their plant-eating counterparts, as spotting prey is crucial for their hunting strategy.
According to a 2020 study published in the Journal of Fish Biology, fish that regularly feed on other fish have larger eyes in proportion to their body size, allowing them to better detect movement in their environment.[1] Some types of predatory fish can also camouflage themselves by changing color to better ambush their prey.
Hunting strategies
Fish that consume other fish display a wide range of hunting techniques tailored to their physical capabilities and habitats. Many are solitary hunters, either lurking in wait of prey or actively pursuing it over short bursts.
Species like barracuda use surprise ambush attacks, hurtling from concealment when target prey comes within close striking distance.
Other predatory fish, including bluefish and rainbow trout, are pack hunters that work together to surround schools of smaller fish, making it harder for victims to escape. A few piscivores even follow in the wake of large aquatic mammals like whales and dolphins, waiting for these larger hunters to flush out fish for them.
Reasons Fish Eat Other Fish
Food and Energy Intake
Piscivory, or the practice of fish eating other fish, is quite common in aquatic ecosystems. Many fish species eat other fish as their main source of food and energy. The calories and nutrients obtained from consuming other fish allows them to grow larger, spawn more eggs, and better survive seasonal shortages of other prey. Research shows that fish growth rates directly correlate with the proportion of fish in their diets.
Population Control
Piscivorous fish also help regulate and control populations of smaller fish species. Without predation to curb their growth, some fish populations would expand rapidly and overrun ecosystems. Predatory fish create selection pressures that keep prey species alert, fast, and adaptable.
This interplay between predators and prey promotes balance and resilience across food webs.
Nutrient Recycling
Fish that eat other fish aid in the recycling and transfer of nutrients between trophic levels. As predators consume and digest prey, nutrients like nitrogen and phosphorus get released back into aquatic systems through excretion and egestion.
These nutrients then become available to algae and plants, fueling ecosystem productivity from the bottom-up. So in many ways, the nutrients within fish get recycled back into fish through the process of piscivory.
To conclude, predation of fish on fish is an integral process regulating populations, energy flow, and nutrient cycling. The behavior likely evolved over millions of years as a adaptation to maximize growth, reproduction, and survival.
As per USGS, over 75% of piscivorous fish tracked showed evidence of eating other fish, proving how widespread this feeding strategy is in freshwater and marine habitats.
Effects on Aquatic Food Chains
Keystone predatory fish
Keystone predatory fish like tuna, salmon, and trout play a crucial role in maintaining balance in aquatic ecosystems. As adults, these fish are apex predators that feed on smaller fish and invertebrates.
Their presence regulates prey populations and prevents overgrazing of vegetation and corals by herbivorous fish. The elimination of keystone predatory fish can trigger trophic cascades and cause widespread ecological changes.
For example, the depletion of large predatory fish in the Black Sea in the 1970s allowed populations of smaller planktivorous fish to boom. These planktivores overgrazed zooplankton, causing phytoplankton blooms and reducing water clarity.
Ultimately, this led to the collapse of the Black Sea’s coral reef ecosystems. Reintroducing keystone predators like sturgeon and turbot is now seen as essential for rehabilitating the Black Sea’s food web.
Impacts of overfishing apex predators
Overfishing of apex predatory fish like sharks, groupers, and snappers can also negatively impact aquatic food chains. A 2016 global analysis found that shark and predatory fish biomass had declined by over 90% in some areas due to overfishing.
This can cause mesopredator release, where smaller predators like rays and smaller grouper species increase in abundance due to reduced predation.
Mesopredators may feed on herbivorous fish, leading to declines in plant-eating fish and the overgrowth of coral reefs by algae. For example, overfishing of sharks in the Caribbean is linked to phase shifts from coral-dominated to algae-dominated reefs.
Protecting apex predators is crucial for maintaining balance in marine food webs.
Invasive piscivorous fish
Invasive piscivorous (fish-eating) fish can also severely disrupt aquatic food chains. Species like lionfish and Nile perch prey on small native fish after being introduced into non-native waters, often causing precipitous declines in prey fish populations.
A classic example is the introduction of Nile perch into Lake Victoria in the 1950s and 1960s, which led to the extinction of around 200 native cichlid species. The ecological impacts cascaded through the food web, reducing phytoplankton and zooplankton abundance and harming fish-eating birds that depended on native cichlids.
Preventing invasions by piscivorous fish is crucial for protecting native aquatic food webs. Where invasions have already occurred, controlling populations of invasive piscivores may help minimize ecological damage.
Conclusion
In conclusion, piscivory is widespread among fish species spanning diverse families, habitats, and traits. Fish eat other fish for crucial nourishment and to regulate balance in aquatic ecosystems. While predatory fish are important keystone species, overfishing and invasive species disrupt delicate food webs.
Understanding fish’s piscivorous tendencies provides key insights into how underwater ecosystems function.