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300



FIGURE 2. Length-frequency distributions of white sturgeon collected with various gear in The
Dalles Reservoir of the Columbia River, 1987.

Angling gear consisted of a medium heavy action rod with a sensitive tip, a
bait casting reel with 18 kg breaking strength monofilament line and 7/0 or 9/0
J-type hooks. Rods were closely attended. Hooks were baited with Pacific
lamprey pieces, coho salmon pieces, whole eulachon, Thaleichthys pacificus,



GEAR SELECTIVITY FOR WHITE STURGEON



177



whole juvenile coho salmon or pickled herring, Clupea sp. We fished from an
anchored boat for durations of 1/2 to 3 h in depths from 15 to 45 m.

We measured fork length of captured white sturgeon to the nearest
centimeter. Hook size and bait type were recorded for all sturgeon caught by
setlines and angling. We also identified and counted the catch of other fish
species.



30 n














10/0


20








— , N - 167


10

















30 1


,












1






hn ^^/°


% ''










N = 197


g 10-
Z 0-


J








~l — . .




^ 30n






\~1 ^*/°


5 20
5 10.

o

oJ

30 1








N = 181


1










y-^






t~n ^^/°


20










N = 186


10








1




nj











1 t=i



100 200

FORK LENGTH (CM)



300



FIGURE 3. Length-frequency distributions of white sturgeon collected with various hook sizes on
setlines in The Dalles Reservoir of the Columbia River, 1987.

We evaluated gear based on harm caused to white sturgeon, sampling
efficiency, size selectivity, and catch of other game fish. Harm was evaluated by
the number of dead white sturgeon in the catch by gear. Sampling efficiency
was evaluated by comparing catch-per-u nit-effort (CPUE) among gears. We
standardize CPUE of gear by calculating mean catch per crew week (40 hours
of sampling by a crew using the gear) based on 13.4 crew weeks of setlining,
3.7 crew weeks of gillnetting and 0.9 crew weeks of angling. We evaluated size
selectivity by comparing length-frequency distributions of catch among gears.
We assumed size selectivity was least where the range of lengths sampled was
greatest. Statistical differences in length frequencies of fish captured among
gears were identified with chi-square tests. We also used chi-square analysis to
test for the selectivity associated with hook size and bait type used while
setlining.



1 78 CALIFORNIA FISH AND GAME

TABLE 1. Summary of white sturgeon effort and catch in The Dalles Reservoir, 1987.

Number of Crew Catch per 40

Gear Observations hours Catch crew hours

Selline 233 538 826 61.4

Cillnet 87 149 184 49.4

Hook and line 25 36 31 34 4



RESULTS

All three gear sampled white sturgeon essentially unharmed. Direct mortality
was only one fish for each gear.

Setlines were the most productive gear (Table 1 ). Catch per crew week with
setlines was 1.24 times catch with gillnets and 1.78 times catch by angling.

TABLE 2. Incidental catch of fish other than sturgeon in The Dalles Reservoir, 1987.

Hook

and

Species Set line Cillnet Line

Carp, Cyprinus carpio 4

Qhar\r[e\ Q&\i\sh, Ictalurus punctatus 1

Chinook salmon, Oncorhynchus tshawytscha 1

Largescale sucker, Catostomus macrocheilus 6

Northern squawfish, Plychocheilus oregonensis 19 14

Sockeye salmon, Oncorhynchus nerka 3

Steelhead, Oncorhynchus mykiss 10

Walleye, Stizostedion vitreum 2

Different gear caught different sizes of fish (Figure 2) and differences were
significant between setlines and gillnets (X*^ = 340.7; df = 7; p <0.01).
Setlines captured white sturgeon over a much wider range of lengths and fish
of a greater length than gillnets. Sample sizes from angling were inadequate to
statistically compare length distribution differences with other gears.

Differences in length-frequency distributions were significant for white
sturgeon captured by various hook sizes (X^ = 88.3; df = 18; p < 0.01)
(Figure 3). Larger hooks took larger fish and fish over a wider range of fork
lengths. White sturgeon greater than 90 cm fork length appeared fully recruited
to all setline hook sizes.

No significant difference in length-frequency distributions was detected
between bait types (X^ = 5.2; df = 5; p = 0.389).

Gillnets frequently caught fish other than sturgeon including several game
species (Table 2). Setlines caught only the nongame northern squawfish. No
other fish were caught while angling for sturgeon.

DISCUSSION

We concluded that setlines were the best available gear for our study. Setlines
caught more white sturgeon per crew hour than the other gears and did not
catch any other game fish. Setlines also appeared to take the most represent-
ative sample of white sturgeon over 90 cm based on length-frequency
distributions of catches. We were primarily concerned with white sturgeon 90
cm and larger, corresponding to lengths harvested in the fisheries, and the
reproductive stock (fish longer than 183 cm, the maximum legal length limit).



GEAR SELECTIVITY FOR WHITE STURGEON 179

The gillnets had many drawbacks and few advantages over setlines. Whereas
white sturgeon mortality was low in gillnets, the nets captured fish other than
sturgeon, particularly adult salmon and steelhead, often with a substantial
mortality rate. This restricted use of gillnets to areas and times where salmon
and steelhead were absent. Gillnets also captured white sturgeon from a
narrower range of lengths than did setlines, and much of the catch consisted of
fish under 90 cm fork length.

Angling was also inferior to setlines. Although mortality was low, the effort
per fish was high. The length range of white sturgeon captured with hook and
line fell within that captured by setlines, although a similar distribution might be
expected with a greater sample size.

We will only sample with setlines for the remainder of the study. However,
we have made a few modifications to address the efficiency and selectivity of
our setlines. We are discontinuing using 10/0 hooks for the following reasons:
(i) they required more crew hours to use because they were harder to sharpen
and bait and required more frequent replacement; (ii) the white sturgeon they
captured were within the range of those captured with 12/0 hooks; and (iii)
these hooks were often straightened out or snapped off, apparently unable to
hold larger fish. We will only use 136-kg test gangions because of the number
of broken 68-kg test gangions observed.

Finally, we will only use Pacific lamprey for bait. Pacific lamprey slices appear
to be an attractive bait for white sturgeon for more than one day. Coho salmon
pieces often fell apart within 24 hours. Further, Pacific lamprey is relatively easy
to obtain and minimizes preparation and gear deployment time.

ACKNOWLEDGMENTS

We thank Doug Engle and Ray FHartlerode for assistance with field sampling.
Bruce Rieman guided this project through its early stages. Wayne Burck, Mary
Buckman, and Tony Nigro provided constructive editorial comments on early
drafts of this manuscript. The Bonneville Power Administration provided
funding for this work under Contract DE-AI79-86BP63584.

LITERATURE CITED

Bajkov, A. D. 1951. Migration of the white sturgeon Acipenser transmontanus in the Columbia River. Fish
Commission of Oregon Research Briefs, 3(2):8-21.

Beamesderfer, R. C, and B. E. Rieman. 1988. Size selectivity and bias in estimates of population statistics of

smallmouth bass, walleye, and northern squawfish in a Columbia River reservoir. No. Am. ). Fish. Mangt.,

8:505-510.
Bosley, C. E. and C. F. Cately. 1 981 . Polychlorinated biphenyls and chlorinated pesticides in Columbia River white

sturgeon Acipenser transmontanus. U.S. Fish and Wildlife Service, Marrowstone Field Station, Nordland,

Washington. Unpublished report.

Cochnauer, T. C. 1983. Abundance, distribution, growth and management of white sturgeon Acipenser
transmontanus in the middle Snake River, Idaho. Doctoral dissertation. University of Idaho.

Coon, ). C, R. R. Ringe, and T. C. Bjornn. 1977. Abundance, growth, distribution and movements of white
sturgeon in the mid-Snake River. Water Resources Research Institute, Research Technical Completion Report,
Project B-026-IDA. University of Idaho. Moscow. 63 p.

Calbreath, ). 1985. Status, life history, and management of Columbia River white sturgeon, Acipenser
transmontanus. Pages 119 to 126 in F. P. Binkowski and S. I. Doroshov, eds. North American sturgeons. Dr.
W. Junk, Dordrecht, The Netherlands.

Haynes, |. M., R. H. Cray, and ). C. Montgomery. 1978. Seasonal movements of white sturgeon (Acipenser
transmontanus) in the mid-Columbia River, Trans. Am. Fish. Soc, 107:275-280.



180 CALIFORNIA FISH AND GAME

Hess, S. S., and S. D. King. 1988. The 1987 lower Columbia River (Bonneville to Astoria) and estuary salmon
(buoy 10) recreational fisheries. Oregon Department of Fish and Wildlife Report. 62 p.

Kohlhorst, D. W. 1980. Recent trends in the white sturgeon population in California's Sacramento-San Joaquin
Estuary. Calif. Fish and Game, 66:210-219.

Lukens, j. R. 1981. Snake River Sturgeon Investigations (Bliss Dam Upstream to Shoshone Falls). Idaho
Department of Fish and Came Report to Idaho Power Company. 33 p.

Oregon Department of Fish and Wildlife. 1988. Columbia River fish runs and fisheries, 1960-87. Portland. 105 p.
Pycha, R. L. 1956. Progress report on white sturgeon studies. Calif. Fish and Game, 42:23-35.
Raymond, H. L. 1988. Effects of hydroelectric development and fisheries enhancement on spring and summer
Chinook and steelhead in the Columbia River basin. No. Am. ). Fish. Mangt , 8:1-24.

Rieman, B. E., ]. C. Elliott, and A. A. Nigro. 1987. Appendix A. Pages 7-24 in Status and habitat requirements of
white sturgeon populations in the Columbia River downsteam from McNary Dam. Bonneville Power
Administration, Annual Progress Report, Portland, Oregon. 60 p.

Semakula, S. N., and P. A. Larkin. 1968. Age, growth, food and yield of the white sturgeon (Acipenser
Iransmontanus) of the Fraser River, British Columbia. ). Fish. Res. Bd. Can., 25:2589-2602.



NOTES 181

Calif. Fish and Game 76 ( 3 ) 1 990

NOTES

GIANT BLUEFIN TUNA OFF SOUTHERN CALIFORNIA,
WITH A NEW CALIFORNIA SIZE RECORD

Most of the Pacific bluefin tuna, Thunnus thynnus orientalis (Temminck and
Schlegel, 1844), landed by purse seiners in the eastern Pacific weigh 5 to 25 kg,
but fish weighing over 50 kg are not uncommon. Exceptionally large bluefin tuna
were caught, mostly in November and December, 1988, by a fleet of small
purse seiners based in San Pedro, California. During the period of 28 October
1 988 to 4 January 1 989, 1 5 boats made 56 trips to areas just south of the east end
of Santa Rosa Island, northwest of San Nicolas Island, and to Tanner and Cortes
banks (Figure 1 ). They captured an estimated 987 fish weighing from about 50
to 458 kg; the total weight was about 139 mt and the average size was about 141
kg. These fish are of special interest because bluefin tuna of this size are of great
value on the Japanese sashimi market, no bluefin of this size had been caught
previously in such quantities in the eastern Pacific, and many of these were
larger than any bluefin caught previously in California.

Meristic characters and morphology were used to verify identification. Gill
raker count on a 242-cm specimen was 13 + 23 = 36, and the ventral surface
of the liver was striated in several specimens, which, coupled with the extreme
size, indicate these fish were not yellowfin tuna, T. albacares. The caudal keels
were usually black or dark grey, indicating that these were not southern bluefin,
T. maccoyii. The pectoral length, as a percentage of fork length, was 16.8% for
the record fish, indicating it was a Pacific bluefin tuna (Gibbs and Collette
1967).

Yukinawa and Yabuta (1967) fitted a von Bertalanffy growth curve to age
data derived from scales of bluefin up to 7 years old from the western Pacific
and extrapolated lengths-at-age to 20 years. From their equation, bluefin of this
size are estimated to be from 5 to 17 years old. Bluefin of the same size from
the Atlantic are estimated by analysis of otoliths (Hurley and lies 1983) to be
7 to 24 years old, although significant variation in age exists among individuals
of the same length and between sexes.

The largest fish (Figure 2) was caught at ca. 0200 h on 18 December 1988,
at San Nicolas Island, by the 21 -m purse seiner SEA QUEEN. It weighed 457.7
kg and measured 271.2 cm fork length (FL). It exceeded the previous California
record (Dotson and Graves 1984) by 220.7 kg, although there is an unsubstan-
tiated record of a 408-kg fish taken in a net in Monterey Bay early in the 20th
century (Holder 1913). The fish was male, appeared robust, and its position
relative to the length-weight curve was well above the rest of the values used
for fitting it (Figure 3).

Large bluefin were initially sighted around 15 October, but were over deep
water and no successful sets were made. On 27-30 October several vessels
caught ca. 63 tons of smaller bluefin (50-70 kg), mostly around Tanner and
Cortes banks. On 30 October, a favorable report from spotter aircraft sent the



182



CALIFORNIA FISH AND CAME



boats north to the relatively shallow (less than 50 fm) area south of East Point
on Santa Rosa Island. As the fish were wild and not catchable during the day,
the boats, assisted by the spotter aircraft, set at night on visible trails caused by
movement of the fish through bioluminescent plankton. The nets of most
vessels in the fleet normally fish at 45-50 fm maximum depth, and unless the
schools were in shallower water, the fish usually escaped underneath or
otherwise evaded the net. Sets were made in water as shallow as 18 fm and as
deep as 100 fm. Catches of the large fish were first made on 31 October and
continued sporadically through December with the last catch occurring on 3
January 1989. Most of the sightings were made between Santa Rosa Island and
Begg Rock.



r ' ' I I ' I ' ' I I '




FIGURE 1 . Areas of catches (crosshatched) of large bluefin tuna captured during November and
December 1988.

Schools such as these are conspicuous during both night and day when near
the surface, and with the aid of fairly constant spotter aircraft activity in previous
years, were seen sporadically in 1986 and 1987, although less frequently than in
1988. Schools were reported from the Sixtymile Bank northwest to the
Rodriguez Seamount but few, if any, were caught. Prior to this season (1988),
spotter aircraft may have ignored large fish in small schools (1-5 fish) because
they were either misidentified as pods of marine mammals or judged unprof-
itable in tonnage. As prices rose dramatically due to interest shown by Japanese
buyers, the spotters and vessels alsobecame interested in the small schools of
larger fish.



NOTES



183




FIGURE 2. The California record bluefin tuna.



Drift gill-net vessels also reported the large fish, although offshore and over
deeper water (greater than 1000 fm), during October-December of 1986, 1987,
and 1988, but caught no bluefin greater than about 50 kg, as the larger fish tore
holes in the nets. During this period of 1988, a gill-net vessel set its gear in the
Santa Rosa Flats area, and the pilot of a spotter aircraft observed a school of
bluefin swim through the net. Subsequent examination of the net revealed
the large holes similar to those evident after fishing in the offshore areas.

The mean weight of the fish caught mostly at Santa Rosa Island during
November (194 kg) was much greater than that of those caught during
December (100 kg), when fishing shifted to San Nicolas Island and Tanner and
Cortes banks. The greatest mean size of fish and smallest number of fish per
successful set (Table 1 ) were captured during the latter half of November,
when a total of 79 fish (6.6 per set) averaged 260 kg for the 2-week period of
18 November-1 December. Calkins (1982) presented length-frequency data by
year for surface-caught bluefin in the eastern Pacific Oceanwhich showed few
instances of fish approaching these sizes.



184



CALIFORNIA FISH AND GAME



500
450




t

w


- T 1 1

-9.02408
eight - e

r^ = .96


2.6767
Length


1 1


T 1

*


-


400


-




n = 38






9^


~


-5^350

^ 300

^250
III

200


-




° .8«r^




CD a^
D


y^


-


150


-




^.^4^°








~


100
en




1


1 1 1


1 1 1


1 1


1 1





160 180 200 220

LENGTH (cm)



240



260



280



FIGURE 3. The length-weight relationship for 38 bluefin tuna captured during Novennber and
December 1988 off Southern California. Record fish indicated by star.



TABLE 1.


Summary of South


ern


California Land


ngs (in Kg)


of Large


Bluefin Tuna Captured Between




28 October 1988 a


nd 3 January


1989.












Week










Total no.


Mean no


Mean wt.


Total


Mean


ending


Area






Trips


offish


of fish


per fish


landings


catch


Nov 3


Tanner, Cortes
banks, Santa Rosa 1.






6


56


9.3


150


8.404


1,401


Nov 10


Santa Rosa 1.






10


189


18.9


178


33,744


3,374


Nov 17


"






5


103


20.6


197


20,284


4,057


Nov 24


"






5


34


6.8


272


9,230


1,846


Dec 1


"






7


45


6.4


251


11,318


1,617


Dec 8


Tanner Bank






5


84


16.8


52


4,385


877


Dec 15


Tanner Bank,
San Nicolas \.






9


287


31.9


126


36,208


4,023


Dec 22


San Nicolas,
Sta. Barbara 1.






5


36


7.2


170


6,107


1,222


Dec 29



























)an 5


Tanner Bank






4


153


38.3


59


9,072*


2,268*



56



987



17.6



141



1 38,753



2,478



TOTAL
* estimated

According to records of the Inter-American Tropical Tuna Commission
(lATTC), catches of large bluefin in the eastern Pacific are rare. During
August-December 1977, fish of about 50 to 110 kg were caught off northern
Baja California by purse seiners. In October 1986, one vessel caught 45 mt of
bluefin in shallow water off Santa Rosa Island, about half of which were
exceptionally large. Fifty of these were measured by the lATTC; their lengths
ranged from 180 to 200 cm (ca. 109 to 145 kg). On 7 December 1981, a single
fish weighing 237 kg was caught in a drift gill-net 12 mi south of Anacapa Island
(Dotson and Graves 1984). The record for bluefin tuna captured in California
waters by a sport angler stood at 113.9 kg from 1899 to 4 October 1983, when
a 164.9-kg fish was captured at Osborn Bank (S.J. Crooke, Calif. Dept. of Fish



NOTES 185

and Game, Long Beach; pers. comm.). Large bluefin tuna are known to occur
in Baja California waters around Guadalupe Island (lat 29°irN, long 118°17'W).
On 21 July 1982, an angler captured a 126.5-kg bluefin and on 22 September, of
that year, a diver speared a 180.5-kg fish at this locale.

Bluefin weighing more than 225 kg occur frequently in Japanese longline
catches in the central and western Pacific. The largest bluefin recorded by the
Far Seas Fisheries Research Laboratory of Shimizu, Japan, weighed about 555 kg
(ca. 3 m). It was caught during April 1986, about 300 mi south of Kyushu Island,
Japan. Large Pacific bluefin also occur occasionally in the southwest Pacific
(Collette and Smith 1981 ). Bluefin between 225 and 450 kg are caught regularly
in the Atlantic, and fish between 450 and 680 kg are sporadically encountered
there (Hisada and Suzuki 1982).

lATTC employees collected biological samples from 62 of the fish and made
abstracts of the logbook records of all the vessels. The mean sea-surface
temperature (for those boats recording it) was 14.rC. Gross examination of
stomach contents during processing revealed that when captured the fish had
been feeding primarily on chub mackerel. Scomber japonicus, and small (10
cm) market squid, Lollgo opalescens, indicating feeding near the surface.

The gonads of 45 fish were examined; all were males. No studies of sex ratios
in large ( > 100 cm) bluefin tuna in the eastern Pacific appear in the literature,
but Yamanaka et al. (1963) note that females predominated in fish sampled by
longline during May and June in the area east of Formosa (Taiwan), and males
in fish sampled around Sanriku during June through August. Rivas ( 1 975 ) found
a preponderance of females in Atlantic bluefin tuna caught in the Straits of
Florida and near the Bahama Islands during April and May, and a preponder-
ance of males in the Gulf of Maine and off Nova Scotia and Newfoundland in
July through October. Although there is an indication of segregation by sex in
these large fish in the eastern Pacific, lack of data from other geographical areas
precludes further speculation.

The reason for the appearance of these exceptionally large fish in the eastern
Pacific is unknown. Immature Pacific bluefin are trans-Pacific migrators
(Orange and Fink 1963, Clemens and Flittner 1969, Bayliff 1980), with a portion
of the population migrating from the western Pacific after the first or second
year of life and staying in the eastern Pacific for up to 2 years or more, before
returning to the western Pacific. Bluefin tagged in the eastern Pacific and
recaptured in the western Pacific were at liberty for a minimum of 22 months
(Clemens and Flittner 1969, Bayliff 1988). There is no evidence of spawning,
e.g. presence of larvae or juveniles or reproductively-active adults, in the
eastern Pacific (Bell 1963). First maturity occurs at 3 to 4 years (Hirota, et al.
1976), and fish older than that (50 to 150 kg) occur in the eastern Pacific at
irregular intervals, especially late in the year around offshore banks, but not
nearly as frequently as do the younger ones. It is not known whether these large
fish were recent arrivals form the western Pacific or had spent several years in
the eastern Pacific.

Ex-vessel price for the vessel owners who sold their catches outright was
$15.40 to $26.40 per kg, although other owners opted to receive a share of the
profits from the sale of the fish in Japan, where prices ranged from $35.20 to
over %77 per kg.



186 CALIFORNIA FISH AND CAME

ACKNOWLEDGMENTS

We thank Bruce B. Collette of the National Museum of Natural History and
W. H. Bayliff of the lATTC for their reviews of the manuscript, Liz Palmer and
Ed Everett for collection of data, and Kurt Schaefer for identification of stomach
contents. We also thank John Huelman, of Ventura, for information on spotter
aircraft activity; Sal Ciaramitaro and John Mattera for anecdotal fishing
information; the staff of United Food Processors of Terminal Island, and the
crews of the San Pedro purse-seine fleet for their cooperation in allowing
collection of catch and biological data.

LITERATURE CITED

Bayliff, W. H. 1980. Synopsis of biological data on the northern bluefin tuna, Thunnus thynnus (Linnaeus, 1758),

in the Pacific Ocean. Inter-Am. Trop. Tuna Comm., Spec. Rep., 2:262-293.
Bell, R. R. 1963. Synopsis of biological data on California bluefin tuna Thunnus saliens Jordan and Evermann 1926.

FAO, Fish. Rep., 6(2):380-^21.

Calkins, T. P. 1982. Observations on the purse-seine fishery for northern bluefin tuna (Thunnus thynnus) in the

eastern Pacific Ocean. Inter-Amer. Trop. Tuna Comm., Bull., 1 8(2) :1 23-225.
Clemens, H. B., and C. A. Flittner. 1969. Bluefin tuna migrate across the Pacific Ocean, Calif. Fish and Game,

55(2);132-135.
Collette, B. B., and B, R. Smith. 1981. Bluefin tuna, Thunnus thynnus orientalis, from the Gulf of Papua. )apan. ).

IchthyoL, 28(2):166-168.
Dotson, R. C, and J. E. Graves. 1984. Biochemical identification of a bluefin tuna establishes a new California size

record. Calif. Fish and Game, 70(1);58-64.
Gibbs, R. H., )r., and B. B. Collette. 1967. Comparative anatomy and systematics of the tunas, genus Thunnus. U.S.

Fish Wildl. Serv., Fish. Bull., 66(1 ):65-130.
Hirota, H., M. Morita, and N. Taniguchi. 1976. An instance of the maturation of 3 full years old bluefin tuna

cultured in the floating net. )ap. Soc. Sci. Fish., Bull., 42(8):939.
Hisada, K., and Z. Suzuki. 1982. Catch, fishing effort and length composition of the Atlantic bluefin caught by the

Japanese longline fishery. Int. Comm. Cons. All. Tunas, Coll. Vol. Sci. Pap., 17(2);307-314.
Holder, C. F. 1913. The game fishes of the world. Hodder and Stoughton, New York. 411 p.
Hurley, P. C. F., and T. D. lies. 1983. Age and growth estimation of Atlantic bluefin tuna, Thunnus thynnus, using

otoliths. Pages 71-75 in E. D. Prince and L. M. Pulos, eds. Proceedings of the international workshop on age


1 2 3 4 6

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