The striped mullet, Mugil cephalus, is found in coastal temperate and tropical waters across the globe. This fish is highly adaptable, exhibiting euryhaline capabilities that allow it to thrive in environments ranging from marine water to brackish estuaries and even freshwater rivers. The striped mullet holds significant economic value as a globally harvested food fish. It plays an important ecological role by linking microscopic food sources to larger predators within the food web.
Primary Dietary Components
The striped mullet is primarily an omnivore, leaning heavily toward detritivory and herbivory in its adult life stage. The bulk of its nourishment comes from consuming organic detritus—decomposing plant and animal matter mixed into the bottom sediment. This material is rich in microbial life, providing a concentrated food source.
The fish actively grazes on microscopic organisms, which constitute a large portion of the digestible matter they ingest. This includes various forms of microscopic algae, such as diatoms and blue-green algae (cyanobacteria). They also filter phytoplankton from the water column.
To acquire these tiny food particles, the mullet actively consumes the top layer of soft sediment, which can often comprise a significant volume of their stomach contents. The sediment itself is not digested, but it serves as a vehicle for the organic matter and microbial communities living within it.
Specialized Feeding Anatomy
The striped mullet possesses several unique anatomical features that enable its specialized feeding method. Its mouth is small and terminally positioned, opening at the front of the head. It is structured for scraping and sucking material directly from hard surfaces or the top layer of soft mud, allowing the fish to efficiently vacuum up the surface film of sediment and attached micro-organisms.
Once water and sediment are drawn in, the fish employs a highly efficient filtering system utilizing its fine, comb-like gill rakers. These projections are located on the gill arches and function as a sieve, straining minute food particles, such as phytoplankton and small detritus, from the water. The dense arrangement of these rakers is an adaptation for filter feeding on extremely small items.
The digestive tract includes a highly muscular, thick-walled stomach structure, called the pyloric stomach, which is often compared to a bird’s gizzard. The sand particles the mullet intentionally ingests act within this organ to physically grind the consumed detritus and the tough cell walls of algae. This mechanical breakdown is necessary to release nutrients for chemical digestion, making the ingested grit an important aid in processing their diet.
Influence of Habitat and Life Stage on Food Choices
The food choices of the striped mullet vary significantly between different life stages and environmental conditions. Larval and small juvenile mullet (typically under 35 millimeters) initially exhibit a more carnivorous diet, feeding primarily on zooplankton and small invertebrates like copepods and mosquito larvae. This shift occurs as the fish grows and develops the specialized anatomical features required for scraping and sediment consumption.
As the mullet mature, their diet shifts almost entirely to sediment-based detritus and microalgae. The specific types of algae consumed are influenced by the environment. For example, mullet in freshwater habitats may ingest more planktonic micro-algae, while those in brackish estuaries consume more benthic micro-algae. Salinity levels and water flow affect the composition of the microbial communities available.
While the adult diet is dominated by plant matter and detritus, the striped mullet is an opportunistic feeder. They may ingest small insect larvae, worms, or bits of plant debris, particularly when primary food sources are limited. This flexibility allows them to exploit a wide range of available food resources within the diverse coastal and estuarine environments they inhabit.