The jack mackerel, Trachurus symmetricus, resource off the

west coast of North America is known to be large and widely

distributed. The spawning biomass is estimated to be 2.1 to 4.8 million tons based upon abundance of jack mackerel eggs collected at sea. The distribution extends from the Gulf of Alaska to the Gulf of Tehuantepec, off the coast of southern Mexico, and as far as 1,500 miles seaward. Within this range lies an area of maximum density which extends from Point Conception to central Baja California.

Jack mackerel biological data has not been processed very

rapidly due to higher priorities for analysis of sardine and

Pacific mackerel data, and the apparent healthy condition of

this resource. The California Department of Fish and Game

initiated several projects in 1972 to resolve unanswered biological questions.  (14pp.

Knaggs, Eric H.

English

Aquatic Commons

STATUS OF THE
JACK MACKEREL RESOURCE
AND ITS MANAGEMENT
by
Eric H. Knaggs
MARINE RESOURCES
TECHNICAL REPORT NO.l1 1973
CALIFORNIA DE PAR TME NT OF FISH A ND GAME
MARINE RESOURCES TECHNICAL REPORTS
******************************************************
Marine Resources Technical Reports are research
documents by Department personnel that are of sufficient
importance to be preserved, but which for some reason
are not appropriate for primary scientific publication. No
restriction is placed on subject matter.
These Reports may be cited in publication, but care
should be taken to indicate their manuscript status. The
material in these Reports may eventually appear in the
primary scientific literature.
Inquiries concerning the Reports should be directed
to The Editor, Marine Resources Region, 350 Golden Shore,
Long Beach, California 90802.
•
THE STATUS OF THE JACK MACKEREL RESOURCE
AND ITS MANAGEMENT
by
Eric H. Knaggs
Marine Resources Region
MARINE RESOURCES TECHNiCAL REPORT NO. 11
California Department of Fish and Game
1973
ABSTRACT
The jack IMckerel, Truchurus symmetricus, resource off the
west coast of North America is known to be large and widely
distributed. The spawning biomass is estimated to be 2.1 to 4.8
million tons based upon abundance of jack mackerel eggs collected
at sea. The distribution extends from the Gulf of Alaska to the
Gulf of Tehuantepec, off the coast of southern Mexico, and as
far as 1,500 miles seaward. Within this range lies an area of
maximum density which extends from Point Conception to central
Baja California.
Jack mackerel biological data has not been processed very
rapidly due to higher priorities for analysis of sardine and
Pacific mackerel data, and the apparent healthy condition of
this resource. The California Department of Fish and Game
initiated several projects in 1972 to resolve unanswered biolog-
ical questions.
(2)
•
TABLE OF CONTENTS
Page
HISTORY OF THE FISHERY----------------------------------------------- 5
BIOLOGICAL KNOWLEDGE------------------------------------------------- 8
REGULATION AND MANAGEMENT--------------------------------------------I0
DISCUSSION-----------------------------------------------------------10
REFERENCES-----------------------------------------------------------11
( 3 )
ACKNOWLEDGMENT
TIlis .study was conducted in cooperation with the Department
of Commerce. National Oceanic and Atmospheric Administration.
National Marine Fisheries Service, under Public Law 88-309,
Project 6-3-R.
-5-
STATUS OF THE JACK MACKEREL RESOURCE
AND ITS MANAGEMENT
by
Eric H. Knaggs
HISTORY OF THE FISHERY
Jack mackerel, Tpachupus symmetPiaus (Ayres), were reported in
the commercial fish catch as early as 1888, but were of minor commer-
cia1 importanc~ until 1947. Most of the jack mackerel catch between
1926 and 1946 was absorbed by fresh fish markets and consisted primarily
of fish taken from mixed sardine, Sapdinops sagax caeruleus~ and
Pacific mackerel, Saomber japonicus~ schools. During these years it
was referred to as "horse mackerel" and had relatively little market
appeal.
During 1947, the industry, after being hit hard by poor sardine
landings, turned to jack mackerel as a substitute sardine and landed
approximately 64,500 short tons. Jack mackerel have been a major con-
tributor to California's connnercial landings ever since, averaging
34,000 short tons annually~
Commercial Fishery
Jack mackerel are caught on southern California fishing grounds
throughout the year by purse seine vessels. In the early days of the
eannery fishery, shortly after 1947, the monthly catches were simply
rel;lted to the activity of the fleet searching for sardines and Pacific
mackerel. As a result, fleet activity was low during the winter and
spring months, reflecting the closed sardine season and spring scarcity
of Pacific mackerel. Current monthly landings do not reflect the clear
Reasonal pattern evidenced in the early days of the fishery (Blunt, 1969).
- 6 -
The southern California wetfish fleet catches jack mackerel from
Point Conception to San Diego, and offshore as far as Tanner and Cortes
Banks.
Offshore distribution of jack mackerel catches over the years has
been related to Pacific mackerel and sardine fishing. During periods
of low sardine and Pacific mackerel catches, the jack mackerel catch
was more seaward. In recent years, with both sardine and Pacific
mackerel catches being under limits or a moratorium, Tanner and Cortes
Banks produced approximately 50% of the jack mackerel catches.
Commercial age and length sampling methods have varied considerably
since 1947 when routine samp1~ng of the cannery catch commenced. These
methods have not always been precise arid systematic, so a new sample
plan was formulated in 1967, and is used at the present time. Funda-
mentally, the sampling is conducted with probability of sampling propor-
tional to estimated weight of a boat load, and with equal probability
for sampling a particular fish within a catch.
Jack mackerel are measured to the closest millimeter fork length
and weighed to the nearest gram. Fish below 200 mm fork length are not
sexed due to the unreliability of determinations on shorter i.ndividuals.
All identification and examination of ovaries is done externally.
Fish caught commercially off southern California and Ensenada are
generally between 50 and 450 mm fork length. Tllese fish are less than
10 years of age. [n recent years, the catch has consjsted primarily
of 0, 1, 2, and 3 year old fish.
Examination of age composition data has shown that domi.nant year
classes are evident in the fishery. The 1947 and 1952 year classes
..
- 7 -
each contributed over 100tOOOtOOO lbs in total landings.
Recreational Fishery
When large jack mackerel are locally abundant t they are much
sought by southern California sportsmen. These fish are caught at or
near the water's surface t usually on a small hook attached to a light
monofilament line. About the only bait that appears to be dependable
is live anchovies. Best fishing occurs from July through September t
but may begin as early as May. Sportfishermen have caught as many as
196,000 large jack mackerel from southern California partyboats during
a single season. Off northern California, large jack mackerel are
considered a nuisance when they take anchovies trolled for salmon
(Frey, 1971).
Jack mackerel also are used by recreational fishermen as live
bait for the larger and more desirable yellowtail, Seriola dorsalis.
In 1935, the California Legislature enacted a bill requiring
I... ritlen catch logs from all partyboat operators. Since 1935, except
for 5 years during World War lIt partyboat catch logs have been collected
un a routine basis.
These records show (1) each day's fishing, (2) area fished, (3)
number of persons fishing t (4) an accurate count of the number of fish
taken, by species, and their approximate weight, and (5) the numbers of
hours of actual fishing, not counting travel time.
Sampling for age composition is not done on a regular basis within
the sports fishery •
~ I
.1
I
I
- 8 -
BIOLOGICAL KNOWLEDGE
Geographic Range
The jack mackerel population represents a renewable resource of
considerable range and magnitude. The distribution extends from the
Gulf of Alaska to the Gulf of Tehuantepec, off the coast of southern
Mexico, and as far as 1,500 miles seaward. Within this range lies an
~rea of maximum density which extends from Point Conception to central
Baja California.
Status of Populations and Subpopulations
An average biomass of 350,000 tons in the California Cooperative
Oceanic Fisheries Investigations (Ca1COFI) survey area was estimated
during the years 1955-57 (MacGregor, 1964). This estimate was based
on egg and larva surveys which did not cover the total jack mackerel
Hpawning range, and included only spawning fish. Consequently, it is
probably a Jow estimate with respect to the total population.
Elbert H. Ahlstrom (1968) estimated the jack mackerel resource
off Califo"rnia and Baja California to range from 1.4 to 2.4 million
tons. The total resource in the eastern Pacific was estimated at
between 2.1 and 4.8 million tons (based on a rough estimate of the total
population as 1 1/2 to 2 times that in the CalCOFI area).
In 1972, the total population off southern California available to
roundhau1 fi.shermen was estimated to range from .7 to 1.5 million tons.
These estimates represent a resource of considerable magnitude.
Migrations
Jack mackerel occurrence in the Gulf of Alaska appears to be
related to warming surface waters with the progression of summer.
-.
- 9 -
The distance traveled by some fish approximates 800 miles at a rate of
13 to 14 miles per day (Blunt, 1969).
It has been hypothesized that juvenile fish from distant offshore
spawning stocks move inshore to grow and develop and then gradually
move seaward again as they become older and larger.
Tagging studies have shown considerable movement of jack mackerel
exists within the California bight area.
Reproduction
Jack mackerel are heterosexual and exhibit sexual dichromatism
during the spawning season.
About 66% of the I year old female jack mackerel are sexually
mature. All female jack mackerel are sexually mature at 3 years of age.
Jack mackerel eggs and larvae are among the more abundant fish
zooplankton in CalCOFI plankton collections. The center of abundance
of the spawning population is off southern California and Baja Califor-
nia between Point Conception and Cape San Quintin. Larvae have been
taken up to 400 miles off the coast of southern California.
Spawning off California and Baja California extends from January
to November. Peak spawning occurs from March to July, when 95% of the
larvae are taken. A single female will normally spawn more than once
during a season and the eggs, which are about 0.98 rom in diameter,
float free in the upper layers of the ocean. The eggs hatch in 4 to 5
days.
Growth
The weight-length relationship derived from our samples is:
W 0.0000042175 L3.16521. This curve is based on a sample of 459 fish.
- 10 -
Mortality
No mortality data are available.
REGULATION AND MANAGEMENT
California has regulations pertaining to fishing gear and craft,
as well as restrictions on commercial fishing in several areas. These
regulations were not passed specifically to control the jack mackerel
fishery and probably have little if any effect on it. There are no
closed seasons or other restrictions on the jack mackerel fishery.
California law prohibits the use of these fish for reduction except
that fish offal may be reduced.
Estimates of the jack mackerel resource represent a renewable
stock of fish with a considerable range and magnitude. Until certain
biological questions concerning jack mackerel are answered, and due to
the apparent healthy condition of this resource; no recommendations
should be made to restrict the use of the jack mackerel resource for
both sport and commercial utilization.
DISCUSSION
Jack mackerel biological data have not been processed very rapidly
due to higher priorities for analysis of sardine and Pacific mackerel
data. Even in some cases, the biological knowledge which has been
obtained is not appropriate for primary scientific publication.
The California Department of Fish and Game initiated several
projects in 1972 dealing with fecundity, migrations, maturation and
growth, age composition of the catch, and population size to resolve
these unanswered biological questions.
- 11 -
Research Needs
To facilitate and stimulate research, problem areas which need to
be an~1ered are outlined below:
a. Stock identification and estimates: Need to determine whether
jack mackerel stock is made up of one or more genetic sub-
populations and what is the distribution, abundance and migra-
.tion. patterns of each.
b. Differential distributions and habits of age groups: Older
fish distributed offshore--fishery depends on younger age
groups, which are available inshore, but what portion of the
total are available to the fishery has yet to be determined.
How much is the varying abundance of young fish dependent on
year class strengths?
c. Analysis and publication of age composition data collected
from jack mackerel fishery since 1947 (in progress but not yet
available).
d. Processing and related problems, especially with regard to the
utilization of older size groups of fi.sh.
e. The decrease in numbers of larger, older fish in commercial
landings during recent years is cause for concern. Does
this represent a decline in the actual size of the breeding
that supports the southern California fishery?
,/
REFERENCES
Ahlstrom, Elbert H. 1968. An evaluation of the fishery resources
available to California fishermen. Tn TIle future of tIle fishing
industry of the United States. DeWitt, Gilbert (Ed.) Univ. Wash.
Publ. in Fish, New Ser., 4:65-80.
- 12 -
Blunt, C.E., Jr. 1969. The jack mackerel (~[1raa(Jhupus symmetraicus)
resource of the eastern North Pacific. Calif. Mar. Res. Comm.,
Ca1COFI Rept., 13:45-52.
Frey, Herbert W. (Ed.) 1971. Jack mackerel. :54-56. In California's
living marine resources and their utilization. Ca1£f. Dept. Fish
and Game, Sacramento. 148 p.
MacGregor, John S. 1966. Synopsis on the biology of the jack mackerel
(r;'rachupus syrronetricus). U.S. Fish and Wild1. Serv., Spec. Sci.
Rept. Fish., (526) :1-16.
8-73 150


Status of the Jack Mackerel resource and its management

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Status of the Jack Mackerel resource and its management

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