Yellowfin Tuna, What Do You Really Know of These Spectacular Fish?

Yellowfin Tuna, What Do You Really Know of These Spectacular Fish?

Written by Stan Gabruk

 Owning Master Baiter´s Sportfishing and Tackle in Puerto Vallarta it seems come summer time everyone walking in my door wants to hook into a Yellowfin Tuna, I don´t blame them. Most people will tell me how they have always wanted the chance to challenge a Monster Yellowfin Tuna on their ¨Bucket List¨.  But other than that, what do you personally know about Yellowfin Tuna? For most of you out there you`re going to say ¨not much ¨.  Well amigos, we´re going to change that, at least a little, right now!   

Yellowfin tuna are pretty much everywhere in the world except the Mediterranean Seas and will migrate between latitudes of approximately 40°N to 35°S, is a highly migratory species but in the Pacific Ocean there is very little evidence of east / west or north / south long range migrations. This means there is little opportunity to intermix species forming sub species. To me this means they follow the bait and water temperatures wit h no specific migration patterns.                 

Yellowfin Tuna have gone by many English language ¨common¨ names which include:  Yellowfin Tuna, Yellow fin tuna, Allison tuna, Long Fin Tunny, Longfin, Pacific Long-Tailed Tuna, and Tuna. Other common names include,  Ahi (Hawaiian), Albacora (Portuguese), Rabil (Spanish), and the list goes on…

Habitat

Yellowfin Tuna prefer it between 65 to 88°F (18-31°C).  I know we have seen YF Tuna sound to 150 feet or deeper to adjust body temperatures to surrounding water temperate as the surface water temps were over 90°F which of course is uncomfortable for them. Yellowfin will stay in an area if there is plenty of bait and clean water. But when Areas like Puerto Vallarta has warm water temperatures YF Tuna will migrate north in to the Cabo San Lucas area where historically water temperatures are slightly cooler than PV. So like we saw in El Nino a few years back, Tuna sounded or moved north to cooler water as an example of this. Normally YF Tuna will go as deep as 330 feet if they have a reason to do so.  Yellowfin tuna's circulatory system acts to retain metabolic heat. This warms their bodies above ambient temperature and allows them to process food and transport oxygen more efficiently. Their ability to stay warm does not match the near warm-blooded bluefin tuna, and as a result, their migration range is more limited by water temperature as I just mentioned. Their sensitivity to cooler temperatures also limits vertical movements to the relatively thin layer between the thermocline and surface.

                                 

Yellowfin Tuna are more likely to ¨School¨ with other species of the same size than their own. Here in the Eastern Pacific off Puerto Vallarta you will find them running with several Dolphin species including Spinner Dolphin. When we see this we know we`ll be catching Football sized Yellowfin at the smallest. Spinners are always our friend here in PV! This example of YF Tuna ¨schooling¨ with other species is not seen anywhere except in this area. The rest of the Pacific, Indian and Atlantic Oceans do not see this which makes this behavior unique.

It  also seems that Yellowfin Tuna tend to school only on the surface, the deeper they are the less likely they are to ¨school¨ and will fragment or scatter.  

                                                           

                                               200 pound Yellowfin Tuna caught in Puerto Vallarta, Felipe Bravo of Gueroazteca

 Distinctive Features

The Yellowfin is a large tuna. Its body deepest under its first dorsal fin, while tapering considerably towards the caudal peduncle. Two dorsal fins are present. In adults, the second dorsal fin is very long, as is the anal fin, which is directly below the second dorsal. These fins become relatively longer in larger individuals. The pectoral fin is also long, reaching beyond the space between the dorsal fins. The caudal peduncle is very slender and includes three sets of keels.  With seven to ten dorsal and ventral finlets are present. A swim bladder is present. The eyes are small; teeth are small and conical.

Below are some descriptions of Tuna species running in the Eastern Pacific.

Coloration

The body is metallic dark blue or greenish above, while the belly and lower sides are silvery white and crossed by many vertical, interrupted lines. Perhaps most distinctly, a golden stripe runs along the side. The second dorsal and anal fins and finlets are bright yellow, and the finlets are bordered by a narrow band of black.

Size, Age, and Growth

The maximum length reported for Yellowfin is 110 inches ( 9ft or280 cm) total length and the maximum weight is 880 lbs. (400 kg). The all-tackle record recognized by the International Game Fish Association (IGFA) is 388 lbs. 8 oz. (176.4 kg). This latter example is more indicative of the common maximum size for the species. But that doesn´t mean there are not larger YF Tuna out there. We have had Yellowfin Tuna larger than 400 lbs boated with our certified scale in Cabo waiting for calibration so nothing official for us. And he 388lb record is suspect since this information is from a few years back.

Food Habits

Primary prey include fish, cephalopods (ceph·a·lo·pod [sef-uh-luh-pod], noun, 1. any mollusk of the class Cephalopoda, having tentacles attached to the head, including the cuttlefish, squid, and octopus.), and crustaceans (crus·ta·cean  [kruh-stey-shuh n] noun, 1.  any chiefly aquatic arthropod of the class Crustacea, typically having the body covered with a hard shell or crust, including the lobsters, shrimps, crabs, barnacles, and wood lice.). A study by Watanabe (1958) found 37 families of fish and 8 orders of invertebrates in Yellowfin stomachs. Fish species consumed by the yellowfin tuna include dolphinfish, pilchard, anchovy, flyingfish, mackerel, lancetfish, and other tunas. Other prey are cuttlefish, squid, octopus, shrimp, lobster, and crabs. Yellowfin are sight-oriented predators, as their feeding tends to occur in surface waters during daylight.

Reproduction

Reproduction occurs year-round, but is most frequent during the summer months in each hemisphere. It is believed that 79°F (26°C) is the lower temperature limit for spawning. In the tropical waters of Mexico and Central America, it has been determined that Yellowfin spawn at least twice a year. Each female spawns several million eggs per year. The juveniles grow quickly, weighing approximately 7.5 pounds (3.4 kg) at 18 months and 140 pounds (63.5 kg) at 4 years.

                                                   

                                                                  Yellowfin tuna larvae:
                                   A. 5.1 mm NL, B. 6.0 mm SL, C. 8.5 mm SL, D. 46.0 mm SL
                                                   (NOAA Tech Memo NMFS-SEFC-240)

Parasites

Yellowfin tuna can host up to 40 parasites including protozoans, digenea (flukes), didymozoidea (tissue flukes), monogenea (gillworms), cestoda (tapeworms), nematoda (roundworms), acanthocephala (spiny-headed worms), and copepods.

Well there are, the basics when it comes to Yellowfin Tuna and how it relates to us as fisherman. Useful information if you are an angler looking for the challenge of boating a Monster Yellowfin Tuna or if you are a lure manufacturer looking to understand what the species prefers when it comes to feeding habits.

Hopefully you know a little more now about Yellowfin Tuna and their habits than you did a few minutes ago….

Written by Stan Gabruk, owner of Master Baiter´s Sportfishing and Tackle