10 Tuna, bluefin
Thunnus thynnus
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SCOMBRIDAE FAMILY; also called Atlantic bluefin tuna, tunny fish, horse-mackerel |
Distinguishing characteristics. One of five tunas known to inhabit our waters, the bluefin is easily distinguished- from albacore and bigeye tunas by its much shorter pectoral fin. Although there is no easy method to separate by external characters a defunct bluefin tuna from a yellowfin tuna of similar status, an examination of the underside of the liver quickly tells a person which of these two he is viewing. In the bluefin tuna the entire liver is darkly streaked with blood vessels, whereas in the yellowfin tuna the liver is unmarked.
Distribution. Although adult bluefin tuna have been captured from Shelikof Strait, Alaska, to Cape San Lucas, Baja California, they seldom abound in the waters north of Los Angeles or south of Magdalena Bay. They and the albacore appear to be the only pelagic, schooling tunas on our coast with a distinct preference for temperate waters. (Their appearance on our coast is seasonable and sporadic. Tagging studies have shown that blue-fin migrates across the Pacific between Japan and our shores.
Life history notes. The largest sport-caught bluefin from our coast is a 251-pounder taken off Santa Catalina Island in 1968. The largest authentic eastern Pacific record is a commercially-caught fish 6 feet 2 inches long to the fork of its tail that weighed 297 pounds. This giant was caught at Guadalupa Island on February 1958. In the Atlantic, bluefin are reported to attain 1,800 pounds or more. Most bluefin caught off our shores range from 10 to 4-5 pounds.
No fish ever has been observed in our waters with what could be considered developing or ripe gonads. And nothing definite is known regarding size and age at maturity, number and size of eggs, and so on.
Examination of a number of stomachs indicate that while in our waters anchovies make up the bulk of the diet. Sanddabs, surf perch and white croakers have also been identified among the remains in their stomachs.
Although they have not been aged reliably, it is believed that they may grow as much as 15 pounds annually during their first three or four years of life.
A number of hooked bluefin tuna are lost to sharks, but aside from these and man no natural enemies are known at the present time.
11 Albacore
Thunnus alalunga ;
SCOMBRIDAE FAMILY;
also called longfin tuna, long-finned tunny
Distinguishing characteristics. The extremely long pectoral fins of the albacore serve to distinguish them from all other tunas found off our coast, except the bigeye. They can be told from the bigeye by their heavily striated liver.
Distribution. Albacore appear to have a distinct preference for temperate waters. Their presence along our coast is seasonal and they always first appear in the southern part of their range. Although there is a record of an albacore from Clarion Island off the coast of Mexico, they are rarely observed or caught south of a line done offshore from Magdalena Bay. In the late summer and fall months of some years they abound off the coast of Alaska. Albacore are pelagic, schooling fish that rarely enter greenish or dirty, inshore or coastal water.
Life history notes. The largest sport-caught fish for which there is a record weighed 66 pounds. A 76-pounder appear to be the commercial weight record on our coast- while a 93-pouncier, taken in the mid-Pacific on longline gear, appears to be the all-time record for the species. The age of a giant such as this is not known, but tagging and length measurement studies indicate that albacore increase in weight in the rate of about six pounds per year, for at-least four or five years. After that, average increment is thought to be progressively less each year. Thus, a 27-pound albacore would be four to five years old and one of 35 pounds would be five or six.
Spawning does not take place along our coast, but there are indications that albacore spawn in the mid-Pacific, mostly north and south of Samoa where juveniles, have been found on many occasions. Large specimens caught north and west of Hawaii during late summer on longline gear have had nearly ripe eggs in their ovaries. These eggs are each about one twenty-fifth of an inch in diameter. Contrary to popular belief, the albacore is not a hybrid or "mule". It is a distinct species capable of spawning and reproducing other albacore.
Tagging studies have revealed that albacore probably are the fish world's greatest migrants and may be the fastest. Several fish tagged on the California coast were recaptured off the coast of Japan nearly 5000 miles away. Other fish tagged on California coast have been recovered north of the Hawaiian Islands. Some have even returned to the California coast where they were retaken a year, and in some cases, two. years later. Albacore tagged north of the Hawaiian Islands have showed up both off our coast and that of Japan.
The food of the albacore varies, depending upon whether they are feeding at the surface or deep and what items are easiest obtained at the time and place the albacore is feeding. A majority of the food consists of small fishes, but at times squid, octopi, shrimp-like and crab-like organisms are extremely important.
Like the bluefin, a number of hooked albacore are lost to sharks, but aside from these and man, no enemies are known to exist at this time.