• Source: Pacific bonito




Species description


Pacific bonito, Sarda lineolata, is a marine species of bonito that is a game fighter but not highly thought of as a food fish. Sarda lineolata was thought to be a subspecies of Sarda chiliensis due to the large separation in their range. However, genetic analysis has shown that they are likely the same species. This fish has been mostly found schooling in the open ocean and live up to depths of 110 meters.
It is colored blue to violet above, with metallic luster becoming silvery ventrally. It has ten or eleven stripes on its back running obliquely from the dorsum forward, and fifteen or more rakers below the angle on the first gill. The first dorsal fin is contiguous with the second and longer than the head. The caudal peduncle is slender, and the body entirely scaled. It has no teeth on the vomer. It has a small keel on either side of the median keel on the sides of the caudal peduncle, and six to eight finlets on the dorsal and ventral surfaces of the caudal peduncle. The maximum length is about 40 inches and weight 25 pounds. Females are larger than males at maturity at around 55 cm vs 50 cm. However, males reach maturity around two years sooner. There are no external differences between males and females of any Sarda.
When off the California coast, it is easy to identify these fish because they are the only tuna-like fish in this area that have dark slanted stripes on their dorsal side.




Distribution



The Pacific Bonito has two separate populations with different ranges. The Northern population is typically found between Southern California and Central Baja California. However, they can be found as far North as Southern Alaska in warmer years. The Southern population can be found off the coast of Northern Peru to Chile. The species can be found up to several hundred miles off the coast, but is most abundant in areas 15 miles or less off the coast.




Behavior


Pacific Bonito usually travel in schools. This species migrates up the coast with the seasons. They can migrate up to 600 miles and move south in the winter where temperatures are warmer and north for the summer.




Diet


Fish and squid are its main diet. Bonitos were found to eat primarily Northern Anchovy. They have also been known to eat rockfish, hake, sardines, saury and mackerel. From January to June, during their spawning season, they have been found to eat equal amounts of mackerel and squid.




Conservation Status


Pacific Bonito are a fast-growing species which makes them more resilient to overfishing. Currently, their population is believed to be in stable condition. Not much information on their status is currently known though and more research will need to be done to know for sure. Estimating the populations of this species is also difficult due to them moving around a lot and quickly.




Human interactions and ecosystem role



It is caught by trolling and still fishing, using feather lures, spoons, or live bait. Although there is not a lot of information about this species’ role in the ocean, it does serve as a food source for predators such as swordfish, bluefin tuna, striped marlin, sea lions, and dolphins as well as some sharks.




Habitat


Mature Pacific Bonito are most commonly found in open ocean environments of up to 300 ft and swim in schools. Younger individuals are more often found in kelp forests where they have places to hide. There is evidence to suggest younger individuals may even be found in harbors and bays.




Lifecycle and Reproduction


Pacific Bonito have an average lifespan of 6-8 years in the wild. Pacific Bonito males reach sexual maturity at one year old whereas it takes females to 3 years to reach sexual maturity. This species has been observed preforming some courtship behavior and has been observed releasing gametes simultaneously after swimming together in a circle. Pacific Bonito can spawn multiple years and begin spawning earlier in the season the older they get. They produce eggs which are free floating and take around three days to hatch. They exhibit slight sexual dimorphism during mating and courtship, but only during those times and are otherwise indistinguishable.




Impacts of Climate Change


In typical years, the Northern part of this species’ population resides in Southern California during spring and summer. They can be found farther north during El Nino, but not during normal years. The changing climate may shift their range further north for the foreseeable future. They may also decide not to travel south at all if waters stay warm enough. Becoming resident, has been witnessed in individuals in this species in the past near powerplants due to the way they kept water warm, so this species becoming resident with increased ocean temperatures is entirely possible.




References


Pacific bonito on FishBase
McClane, Albert Jules (1951). The Wise Fishermen's Encyclopedia. New York, USA: William H. Wise & Co.

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