If you read the title and thought to yourself “Wait, there’s a difference?” you are not alone. The names “bonito,” “skipjack,” and “little tunny” (and even “false albacore”) are used almost interchangeably everywhere from colloquially to online resources claiming to be experts.
For those of you who have fallen into the rabbit hole trying to figure it out for yourself, I am here to tell you I’ve fallen in and survived the climb back out, and am ready to tell the tale. Below are the answers to all your questions on who these fish are, why they’re so often confused with one another, and what the final word is on their differences.
Bonito, skipjack tuna, and little tunny are all marine fish that are members of the same sub-family, called Scombrinae. Scombrinae are ray-finned, bony fishes that include four “tribes”: Mackerels, Spanish Mackerels, Bonitos, and Tunas.
All members of this sub-family (Scombrinae) have a tapered - almost bullet-shaped - muscular body that makes them fast swimmers and ferocious fighters when caught. They are all at least semi-migratory while following prey, and are fished both commercially and recreationally. They also all have two dorsal fins (one that is spiny and one that is soft) as well as having somewhere between a deeply forked and a lunate (semi-forked) tailfin.
In general, skipjack tuna, bonito, and little tunny can all be found in temperate to tropical waters in the Atlantic, Pacific, and Indian Oceans and their surrounding gulfs and seas. They are all pelagic, meaning they tend to inhabit the upper layers of the open sea, not too close to the seafloor or the shore.
If you want to get into the specifics of each species, however, it does get more complicated than this.
Bonito actually represent an entire tribe of the Scombrinae sub-family, not a specific species (like skipjack tuna or little tunny do). The scientific name for the bonito tribe is Sardini, which is then broken down into four generas containing eight species. This includes the Australian, Eastern Pacific, Pacific, striped, Atlantic, leaping, and plain bonito, as well as the dogtooth tuna (which is not a member of the tuna tribe itself. Also confusing, we know. That’s for a separate blog post).
The Australian, Eastern Pacific, Pacific, and Atlantic bonitos can be found in the tropical and temperate waters of the regions they’re named after. Striped bonitos can be found in the Atlantic and the Pacific oceans. Leaping bonitos are found near Australia and New Guinea. Dogtooth tuna are found in the Indian and Pacific oceans.
Skipjack Tuna are found in the temperate and tropical waters of the Atlantic, Pacific, and Indian oceans.
Little Tunny are found only in the Atlantic.
Did you notice that many of the regions bonito, skipjack, and little tunny live in are large and overlapping? This is part of what makes it so difficult to distinguish between them, and why their names are used so interchangeably by locals.
On top of that, being that they are all schooling fish that reside in similar areas of the water column in the same waters and hunt the same types of prey, they tend to school together! So really you could be fishing in a school of several types of bonito and skipjack tuna and little tunny at the same time. Very similar to lunch time at the family reunion: you’re probably going to get confused as to which cousin is which when everyone looks pretty similar and they’re all rushing for the same food!
Skipjack, arctic bonito, banjo, lesser tunny, false albacore, mushmouth, ocean bonito, oceanic skipjack, skipper, skippy, stripe bellied bonito, false albacore, striped bellied tunny, striped tunny, victor fish, watermelon, and white bonito. We’ve all heard these nicknames and real names used interchangeably. Are these all the same fish or not? What is accurate, and why?
When it comes down to the nitty gritty of it all, there are many subtle differences between the 8 species of bonito, the skipjack tuna, and the little tunny or false albacore. Their anatomical differences such as having or lacking notches in their hypural plate, having or lacking a bony lateral keel on the posterior caudal vertebrae, differences in circulatory systems, and more are what separate each species within their genera and tribes.
However, instead of giving you a science lesson, which would probably have you asleep before you even got the answers you were looking for, let’s break it down instead by some of the differences that you can observe as an interested, everyday angler.
One of the biggest differences here, as mentioned above, is that bonito is actually a tribe of fish that break down into eight different species, whereas skipjack tuna and little tunny are specific species within the Thunnus tribe, commonly called tunas. This makes distinguishing bonito themselves a little more difficult, as each species has slightly different markings and characteristics.
Something that makes the bonito tribe unique among the Scombrinae sub-family is that it contains one species that has a swim bladder, whereas every other species does not. This is significant because all of the species that lack a swim bladder need to constantly be swimming in order to maintain basic functions such as buoyancy in the water.
Another way to distinguish bonito from these two tunas is that bonito all have some form of stripes along their back and/or sides. These stripes can range in color, thickness, shape, and design, but they will be there. Their anal fin (the fin that is furthest back on their bellies) is further up than that of the little tunny and skipjack. They also have a deeply forked tail fin.
Their meat also contains a very moderate fat content, compared to those of the tuna tribe, who has a much lighter content. That being said, different species of young bonito have very similar flesh to that of a skipjack tuna, and are often used as a substitution in canning.
Skipjack tuna and little tunny are both species within the tuna, or Thunnus, tribe, but belong to two different genera within it. Skipjack tuna (K. pelamis) are part of their own genus, Katsuwonus, whereas little tunny (E. alletteratus) share the genus Euthynnus with mackerel tuna and black skipjack tuna.
Something that makes these two tuna, and all tuna, different from bonito is that they can maintain a body temperature higher than the water they’re in. This helps to increase their swimming speeds, lower energy expenditure, and survive in cooler water temperatures.
Both also have a metallic dark or blue dorsal side that fades to a silver or white belly, which is a pattern used as camouflage. They also have a lunate, or semi-forked, tail fin. Skipjack tuna will have seven to nine finlets between their dorsal and tail fine, whereas little tunny will have eight.
Their meat is much lower in fat content than that of adult bonitos. They both have a darker coloring to their meat, ranging from dark pink to red. Though, their preference as table fare can range regionally. Skipjack tuna is a pretty standard choice for canning worldwide, whereas little tunny is not as widely liked. It is recommended that if you are to consume, they should be bled immediately and prepared as fresh as possible. In fact, little tunny is regarded as excellent sushi grade tuna when prepared correctly.
Just kidding...haven’t we been through enough already?
Now that you have the breakdown of what and where these different species are, the best way to put this knowledge into practice is to go and catch them yourself! Give us a call and we can help you find the best trip that fits the location to help you tighten some lines on false albacore, skippys, or whatever the locals call them in whichever ocean you’d like to go!