Bonito are a group of predatory marine species found worldwide in temperate and tropical waters. These swift swimmers are known for their streamlined bodies. The term “bonito” encompasses several distinct species, leading to common questions about their size. This article clarifies their typical dimensions and the factors influencing their growth.
Understanding Bonito Size
Bonito are medium-sized predatory fish, with dimensions varying by species. Most mature bonito range from 20 to 40 inches (50 to 102 cm) in length. Their weight typically falls between 5 and 25 pounds (2.3 to 11.3 kg). Maximum recorded sizes can be larger for some species.
For instance, Atlantic bonito (Sarda sarda) reach 30 to 36 inches (76 to 91 cm) and 12 to 24 pounds (5.4 to 11 kg). Pacific bonito (Sarda chiliensis) can grow larger, sometimes reaching 31 to 48 inches (79 to 122 cm) and up to 25 pounds (11.3 kg). Striped bonito (Sarda orientalis) are commonly around 22 inches (55 cm) and over 22 pounds (10 kg), though recorded up to 40 inches (102 cm). Australian bonito (Sarda australis) commonly measure 16 to 18 inches (40-45 cm) and weigh 4 to 5 pounds (1.8-2.3 kg), with maximums reaching 71 inches (180 cm) and 21 pounds (9.4 kg).
Factors Influencing Bonito Size
Several biological and environmental factors contribute to bonito size. Species is the most significant factor, as “bonito” refers to a tribe within the Scombridae family with varied genetic growth potential. For example, dogtooth tuna, a bonito tribe member, can reach 100 inches (250 cm) and 250 pounds (113 kg). In contrast, the leaping bonito is one of the smallest, typically around 20 inches (50 cm) and 5 pounds (2.3 kg).
Diet plays a substantial role in their growth. Bonito are carnivorous predators, feeding on smaller fish like anchovies, sardines, herring, and mackerel, along with squid and other invertebrates. An abundant food supply allows for quicker growth and larger sizes. Habitat also influences development; they prefer warm temperate and tropical waters. Younger bonito may stay closer to shore, while larger adults move to deeper, offshore environments.
Age is directly correlated with size, as bonito grow throughout their lifespan. Most species live for 6 to 8 years, though some can reach 12 years. They generally reach sexual maturity around two years of age, with rapid growth in early years that slows with age.
How Bonito Compare to Similar Fish
Bonito are often compared to tuna and mackerel due to their shared family (Scombridae) and similar appearances. However, distinct differences exist in size and physical characteristics. While bonito resemble tuna, they are generally smaller and leaner. Tuna species, particularly bluefin tuna, can be significantly larger, reaching over 600 kilograms (1,300 pounds) and 4 meters (13 feet). Bonito rarely exceed 30 kilograms (66 pounds) and 1 meter (3.3 feet).
Bonito have distinct dark, narrow stripes on their backs, which can be longitudinal or slightly oblique, and silvery undersides. Mackerel often have different spot or stripe patterns; for example, Spanish mackerel have golden spots, and false albacore have squiggly markings. Bonito also possess a more compressed body compared to the more robust tuna. Their sleek, torpedo-shaped bodies contribute to their speed. These features help distinguish them from smaller tuna or larger mackerel.