Do Brine Shrimp Eat Each Other?

Brine shrimp, also known as Artemia, are small crustaceans that live in salty bodies of water like inland salt lakes and coastal lagoons These tiny animals play an important role in aquatic ecosystems and are also popular as fish food in aquaculture and the aquarium trade. But one question that often comes up is do brine shrimp eat each other?

The short answer is yes, under certain circumstances, brine shrimp will resort to cannibalism and eat each other. However, this behavior is not their normal mode of feeding and happens when brine shrimp are stressed due to lack of food or overcrowding.

Normal Feeding Habits of Brine Shrimp

In their natural habitat brine shrimp feed on tiny floating organisms called plankton which includes algae, bacteria, protozoa and small crustaceans. They eat by filtering these microorganisms from the water using their legs which function like tiny oars.

Brine shrimp are non-selective filter feeders and do not actively hunt down prey. They do not normally consume other brine shrimp as part of their natural diet. Instead, Artemia shrimp coexist peacefully together while grazing on the rich soup of plankton available in their hypersaline environment.

When Do Brine Shrimp Resort to Cannibalism?

Under regular conditions with adequate food availability, brine shrimp do not exhibit cannibalistic tendencies However, in laboratory cultures or artificial environments like fish hatcheries, overcrowding and limited food supply can trigger cannibalism among brine shrimp populations

When deprived of sufficient planktonic food sources, brine shrimp become stressed and can attack each other. The shrimp will nip off pieces of their brethren or consume smaller individuals whole. This allows them to obtain nutrition when faced with starvation.

Cannibalism rates tend to escalate with increased stocking densities of brine shrimp. As overcrowding limits food availability per individual, the shrimp are more likely to eat each other to survive. High densities also increase contact between shrimp, raising chances of encounters that can lead to cannibalism.

In fish hatcheries, cannibalism among brine shrimp can cause substantial losses in Artemia nauplii production. Hatchery managers need to optimize stocking rates and feeding levels to minimize cannibalism. Adding more food or harvesting shrimp frequently helps reduce cannibalism triggered by overcrowding and hunger.

Other Factors That Can Stimulate Cannibalism

While lack of food and overcrowding are the main triggers, other factors can also elevate cannibalism risk among brine shrimp populations:

• Presence of dead or dying shrimp: Dead or moribund shrimp are easy targets for cannibalism by healthy individuals. Removal of dead shrimp helps decrease this risk.

• Limited oxygen levels: Low oxygen can stress shrimp and make them more aggressive toward each other. Adequate aeration reduces cannibalism linked to oxygen deficiency.

• High ammonia/nitrite: Poor water quality stresses shrimp and promotes cannibalism. Regular water changes keep water parameters in optimal ranges.

• Bright lighting: Brine shrimp tend to exhibit more cannibalism under bright light than dim or dark conditions. Subdued lighting helps curb cannibalistic behavior.

• Instar differences: Later larval stages and adults are more likely to consume smaller nauplii and early instars. Size gradation reduces cannibalism between developmental stages.

• Predator cues: Chemical signals from predatory fish can trigger higher cannibalism rates among brine shrimp. Isolation from fish reduces this stimulatory effect of predator kairomones.

Thus while overcrowding and limited food are the primary reasons brine shrimp eat each other, other environmental stressors can also elicit cannibalistic tendencies in Artemia populations. Careful management of culture conditions is key to controlling unwanted cannibalism.

Do Brine Shrimp Eat Each Other in Aquariums?

Brine shrimp hatched in small desktop hatcheries are commonly used as live food for aquarium fish and invertebrates. Due to the high densities of nauplii produced, cannibalism can sometimes occur in these hatcheries. Newly hatched nauplii may get consumed by larger larvae or swimming adults.

To minimize losses, brine shrimp are harvested within 24-36 hours after hatching, before substantial cannibalism can occur. Using a lamp or airstone to concentrate the nauplii also expedites harvest and reduces cannibalism risk. Adding products like egg yolk or baker’s yeast can also increase food availability and divert the shrimp from cannibalism.

Once introduced into the aquarium, brine shrimp are less likely to eat each other due to lower stocking densities and availability of other foods like microalgae and detritus. Healthy fish will quickly consume the live brine shrimp as well, giving little opportunity for the shrimp to cannibalize each other.

However, uneaten adult brine shrimp may attack younger nauplii if they coexist in the aquarium for too long. As in production hatcheries, size gradation and prompt harvesting help avoid significant cannibalism issues. Providing adequate alternative foods for the brine shrimp also discourages any tendencies toward cannibalism.

How to Prevent Cannibalism in Brine Shrimp Cultures

While some degree of cannibalism may be inevitable at high densities, the following strategies can help reduce brine shrimp eating each other in mass cultures or small home hatcheries:

• Maintain optimum stocking densities based on food supply and culture system capacity. Overcrowding is a major trigger of cannibalism.

• Provide adequate microalgae levels for food. Increase algae density or supplement with yeast, wheat flour, rice bran or egg yolk to compensate if algae levels are inadequate.

• Change water frequently to remove waste products and maintain water quality.

• Ensure sufficient aeration. Low oxygen promotes cannibalism.

• Cull dead or dying shrimp promptly as they can trigger cannibalism.

• Size-grade populations to segregate nauplii, small and large larvae. This reduces cannibalism between different-sized individuals.

• Harvest shrimp regularly to prevent overcrowding and size differences from increasing. Frequent partial harvests are better than allowing populations to peak.

• Keep cultures in dim light or darkness. Bright illumination exacerbates cannibalism.

• Use separate culture vessels for adults to prevent them preying on nauplii. Adults and larvae should be size-graded.

• Isolate cultures from fish or crustaceans that may release chemicals stimulating cannibalism.

By optimizing conditions and preventing stressors that stimulate cannibalism, Artemia shrimp producers and aquarists can successfully rear brine shrimp without them resorting to eating each other. While cannibalism cannot be fully prevented under intense culture conditions, proper management minimizes losses from this behavior.