The diet of a lobster is not fixed throughout its lifespan; instead, it shifts dramatically as the animal grows and transforms. Lobsters begin life as tiny, free-floating organisms in the water column and later become large, heavy-clawed creatures dwelling on the ocean floor. This fundamental change in habitat and physical structure dictates a complete overhaul of their nutritional needs and feeding strategies. The question of whether lobsters eat zooplankton depends entirely on which phase of their complex life cycle is being examined.
Defining Zooplankton and Lobster Life Stages
Zooplankton are a diverse collection of tiny, non-photosynthetic animals that drift in the water column, ranging from microscopic single-celled organisms to the larval stages of larger marine creatures. These organisms form the base of the pelagic, or open-water, food web. A lobster’s life cycle is characterized by metamorphosis, which is central to understanding its diet.
The initial phase is the planktonic larval stage, where the young lobster is small, often transparent, and floats near the ocean surface for several weeks, dependent on the currents. Larvae pass through three distinct stages before a final molt transforms them into a post-larval or juvenile form. This final stage marks the switch to the benthic, or bottom-dwelling, lifestyle that defines adult lobsters. The physical characteristics of the small larvae limit them to consuming only the smallest available food sources.
Larval Diet: The Zooplankton Connection
Newly hatched lobster larvae rely heavily on zooplankton, which provides the high-protein, high-energy fuel necessary for their rapid growth and development. These tiny larvae are active predators, capturing individual prey items rather than solely filtering water. Their primary food source in the wild consists of various zooplankton species, including copepods and other small crustaceans.
Research has confirmed that a preferred prey for American lobster larvae is the copepod Calanus finmarchicus, a lipid-rich species. The consumption of this specific, nutrient-dense zooplankton is important for the larvae to successfully complete their transformation into the post-larval stage. Larval lobsters also consume other tiny, soft-bodied organisms from the plankton, such as fish eggs and gelatinous zooplankton. Food availability is a major factor in the survival rate of the young lobsters before they settle.
Adult Diet: Scavengers and Benthic Hunters
Once the lobster completes its metamorphosis and settles onto the ocean floor, its diet shifts completely away from zooplankton. The adult lobster is a benthic generalist, meaning it is an opportunistic hunter and scavenger that feeds on what is available in its bottom habitat. This new diet is dictated by the lobster’s larger size, powerful claws, and life on the substrate.
The primary components of the adult diet include hard-shelled benthic invertebrates, such as mussels, clams, sea urchins, and crabs. Adult lobsters use their specialized claws—one for crushing and one for cutting—to break open the shells of their prey. They also act as scavengers, readily consuming dead fish or other carrion they encounter on the ocean floor. This scavenging behavior makes them an important part of the marine ecosystem’s cleanup crew.
The adult lobster’s physiology and feeding strategy are entirely unsuitable for capturing the microscopic organisms that comprise zooplankton. The shift from a pelagic, plankton-eating larva to a benthic, hard-shelled prey consumer is one of the most drastic dietary changes in the entire marine animal kingdom. The juvenile and adult phases focus on consuming a diverse range of bottom-dwelling food items that provide the bulk and nutrients required to support their large, muscular bodies.