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CAUFDRNIA
FBH^GAME

"CONSERVATION OF WILD LIFE THROUGH EDUCATION"




California Fish and Game is published quarterly by the California Department of
Fish and Game. It is a journal devoted to the conservation and understanding of fish
and wildlife. If its contents are reproduced elsewhere, the authors and the California
Department of Fish and Game would appreciate being acknowledged.

Subscriptions may be obtained at the rate of $10 per year by placing an order with
the Editor, California Department of Fish and Game, 1416 Ninth Street, Sacramento.
CA 95814. Checks or money orders in U.S. dollars should be made out to: California
Fish and Game. Inquiries regarding paid subscriptions should be directed to the
Editor. Complimentary subscriptions are granted on an exchange basis.

California Department of Fish and Game employees may request complimentary
subscriptions to the journal.



Please direct correspondence to:

Dr. Eric R. Loft, Editor-in-Chief
California Fish and Game
1416 Ninth Street
Sacramento, California 95814




u




VOLUME 80



SPRING 1994



NUMBER 2




Published Quarterly by



STATE OF CALIFORNIA

THE RESOURCES AGENCY

DEPARTMENT OF FISH AND GAME

-LDA-



STATE OF CALIFORNIA
PETE WILSON, Governor

THE RESOURCES AGENCY
DOUGLAS P. WHEELER, Secretary for Resources



FISH AND GAME COMMISSION

Frank D. Boren, President

Doug McGeoghegan, Member

Richard Thieriot, Member

Gus Owen, Member

Robert R. Treanor, Executive Director

DEPARTMENT OF FISH AND GAME

BOYD GIBBONS, Director

John H. Sullivan, Chief Deputy Director

Al Petrovich Jr., Deputy Director

Banky E. Curtis, Deputy Director

Perry L. Herrgesell, Ph.D., Cliief Bay-Delta Division

Rolf Mall, Ctiief Marine Resources Division

Tim Farley, Cliief Inland Fisheries Division

Terry M. Mansfield, Ctiief Wildlife Management Division

John Turner, Chiief Environmental Services Division

Susan A. Cochrane, Ctiief Natural Heritage Division

DeWayne Johnston, Chief Wildlife Protection Division

Richard Elliott, Regional Manager Redding

Ryan Broddhck, Regional Manager Rancho Cordova

Bhan F. Hunter, Regional Manager Yountville

George D. Nokes, Regional Manager Fresno

Fred Worthley, Regional Manager Long Beach

CALIFORNIA FISH AND GAME
1994 EDITORIAL STAFF

Eric R. Loft, Editor-in-Chief Wildlife Management

Betsy C. Bolster, Ralph Carpenter,

Arthur C. Knutson, Jr Inland Fisheries

Dan Yparraguirre Wildlife Management

Steve Crooke, Doyle Hanan, Jerome D. Spratt Marine Resources

Donald E. Stevens Bay-Delta

Peter T. Phillips Environmental Services



CONTENTS

Relationship Between Sea Otter Range Expansion and Red
Abalone Abundance and Size Distribution in Central California ....
Fred Wendell 45

The Effect of Different Han/est Methods on Sea Palm {Postelsia
palmaeformis) Sporophyll Growth Peter E. Kalvass 57

Duck and Shorebird Reproduction in the Grasslands of Central
California Roger L Hothem and Daniel Welsh 68

Roosevelt Elk Dietary Quality in Northern Coastal California

Peter J. Gogan and Reginald H. Barrett 80

NOTES

A Portable Field Sampling Table for Dock-side Sampling of Fish ....
Robert R. Leos 84



CALIFORNIA FISH AND GAME
Calif. Fish and Game (80)2:45-56 1 994

RELATIONSHIP BETWEEN SEA OTTER RANGE

EXPANSION AND RED ABALONE ABUNDANCE AND SIZE

DISTRIBUTION IN CENTRAL CALIFORNIA

FRED WENDELL

Marine Resources Division

California Department of Fish and Game

213 Beach Street

Morro Bay, CA 93442

Red abalone population surveys were conducted near Point Estero,
California between 1 965 and 1 993, before, during, and after reoccupation
of the area by sea otters. A decline in abalone density occurred (0.1 01 /m^
to 0.007/m^) associated with the reoccupation of the area by sea otters.
Evidence is presented suggesting that sea otter predation was responsible
for the decline and subsequent stability at densities below those needed
to support a viable commercial or recreational fishery.

INTRODUCTION

Sea otters (Enhydra lutris) were over-exploited throughout the North Pacific rim
during the 18"' and 19"" century fur trade era (Ogden 1941). Only a few remnant
colonies survived that era, with as few as 50 sea otters surviving in California (Kenyon
1969). Many of the colonies are gradually expanding their range under protection of
both state and federal law.

Range expansion in California has coincided with the loss of commercial and
recreational shellfish fisheries (Wild and Ames 1974, Miller et al. 1975, Wendell et
al. 1986). Although sea otter effects on nearshore marine community structure are
generally recognized (McLean 1962, Estes and Palmisano 1974, Dayton 1975, Foster
et al. 1 979, Duggins 1 980), their effects on shellfish fisheries have been controversial
(Estes and VanBlaricom 1985).

The controversy exists because of the difficulty in assessing the magnitude of the
effects of sea otter predation and human harvest in the loss of fisheries. A historical
review of shellfish fisheries beyond the sea otter's range emphasized their loss from
over-exploitation (Estes and VanBlaricom 1985). The review expressed doubts about
the relative effects of human harvest and sea otter predation in the loss of the central
California red abalone fishery.

The sport and commercial red abalone fisheries in central California were the first
to experience competition with foraging sea otters. Most of the research that focused
on the relationship between sea otters and abalone abundance lacked information on
pre-reoccupation densities. The earliest research assessed sea otter effects by comparing
abalone abundance between areas with and without sea otters (Ebert 1968). Most
subsequent research focused on population dynamics over longer time periods within
small study areas already occupied by sea otters (Lowry and Pearse 1973, Cooper et
al. 1977, Hines and Pearse 1982, Ostfeld 1982).

45



46



CALIFORNIA FISH AND GAME



Here, data on abalone abundance and size distribution are analyzed that were
collected intermittently over a long time period that included both pre- and post-
reoccupation intervals within a relatively large study area. The original objective of
the study was to monitor abalone abundance and population structure in an area
important to the commercial fishery. After the loss of the fishery, the objective
changed to monitoring the immediate and long-term effects of sea otter predation on
abalone abundance and population structure (E. Ebert, California Department of Fish
and Game, pers. comni.).

METHODS

The Point Estero study area (lat 35 3()'N, long 121 02'30"W) is approximately 20
km north of Morro Bay, California (Fig. 1 ). The area is characterized by low profile
reefs, averaging 2 to 3 m high, aligned nearly perpendicular to the shoreline and spaced
about 1 5 to 60 m apart. Interspersed are gullies or pavement-like substrate strewn with
cobbles and boulders. Sand intrusions frequently isolate rocky outcroppings, particularly




Figure 1 . Spatial relationship of the Point Estero red abalone study area (darkened area) and
location of the southernmost sea otter rafting site (circles) by selected year. Sampling strata
shown in lower left insert.



RELATIONSHIP BETWEEN SEA OTTER AND RED ABALONE 47

in shallower depth zones.

Ocean depths within the 2.4 km long by 0.8 km wide study area ranged from 5.5
m to 22.0 m. The area was divided into five strata arranged from south to north (Fig.
1 ). Strata boundaries were selected to provide comparable depth distributions among
strata. Each strata was divided into sampling units (transect areas) measuring 4.6 x
30.5 m each. Four of the strata (II-V) each contained 3,750 sampling units. Strata I
contained 3,000 sampling units. Thus, the entire study area was potentially available
for sampling.

Sampling effort was evenly distributed among strata and transects were selected
randomly within strata. Each potential sampling unit was numbered and a random
number generator was used to select those to be sampled. Initially, 15 transects were
sampled per annual survey (3/strata). In 1967, the annual sampling effort was
increased to 25 transects. Transects were located using triangulation from existing and
fabricated shoreline markers and laid on a 290 bearing (i.e., parallel to the shore line).

Abalone were identified by species when possible and counted by SCUBA divers.
Some abalone, particularly those observed within narrow crevices, were not identifiable.
Species other than red abalone (Haliotis rufescens) were present in very small
numbers and when identified were excluded from data analysis. Accessible individuals
were removed and measured to the nearest millimeter across the longest dimension of
the shell and replaced within the transect area. The sizes of inaccessible individuals
were visually estimated and assigned to one of three size groups (< 1 02, 1 02- 1 96, > 1 96
mm).

Population estimates were generated based on a simple random sampling design.
Estimates are calculated by multiplying the mean count per transect by the potential
number of transects within the survey area.

Sea otter densities and spatial distributions were assessed using aerial survey data.
Emphasis, for this paper, was placed on aerial surveys conducted during the period
when sea otters expanded their range into the vicinity of the study area. Range
expansion in California has typically been defined by changes in the location of the
southern- and northern-most large sea otter raft. However, a range boundary identified
by this criterion does not recognize that foraging activity occurs beyond the raft
location. Foraging activity can be located several miles beyond the raft site (Wild and
Ames 1974).

Prey selection by sea otters was assessed using data collected during a food habit
study conducted within the Point Estero area in 1971 and 1972 (Wild and Ames 1974).
Observations were made from shore using telescopes ranging from 15x to 60x. Food
items were identified to the lowest taxon possible.

RESULTS

Surveys were conducted in 1965, 1966, 1967, 1970, 1971, 1973, 1974, 1978, and
1993. A total of 205 transects were sampled during the nine surveys. The proportion
of sand on a transect and the water depth were covariates in the study design. For all
survey years combined, both showed statistically significant negative correlations



48 CALIFORNIA FISH AND GAME



with red abalone abundance (Spearman rank (/) values of -0. 1 76, F <0.05 and -0.326,
P < 0.0 1 , respectively). However, no temporal trends were apparent in the distribution
of transect substrate types (r = 0.054, P > 0.05 ) or depths (r = 0. 1 29, A* > 0.05 ) through
the study period. The test for heterogeneity of slopes among years in an analysis of
covariance showed water depth (P = 0.0096) and proportion of sand (P = 0.0025) to
be heterogeneous among years.

There was a temporal trend in the abundance of red abalone within the study area;
the estimated population size declined through time (Table 1 ). There was a statistically
significant negative correlation (/• = -0.901, P < 0.01) between median red abalone
counts and survey year. The main effect of survey year in the analysis of covariance
was highly significant {P < 0.0005).

Both mean red abalone count per transect and mean counts adjusted for the
covariates declined rapidly starting in 1967 (Fig. 2). The average red abalone density
prior to 1967 was 0.100 abalone/m-, declined to 0.010 abalone/m- by 1973, and
remained below that level for all subsequent surveys (Table 1 ). A Kruskal-Wallis
multiple pairwise comparison showed counts from all years after 1973 to be significantly
different from those that preceded at an experimentwise error rate of 0. 1 5. Some pairs
comparing 1971 with earlier years were also significantly different.

The estimated red abalone population size within the study area decreased by 84
percent within six years, and stabilized within eight years at seven percent of the initial
( 1 965 ) estimate (Fig. 3 ). The population estimates during 1 978 and 1 993 suggest that
the resource remained relatively unchanged during the 19-year period from 1974 to
1993.

The decline in abundance appears to have occurred progressively from north to
south within the study area. The mean count declined below 10 abalone/transect
between the 1965 and 1966 surveys within the northernmost strata (V), followed
progressively within strata IV (after 1966), strata III ( 1 967), and strata's II and I ( 1 970)
(Fig. 4). Although multiple pairwise comparisons between years within strata did
demonstrate differences between pairs, the resolution was not sufficient to place

Table 1 . Red abalone density (/m-) and estimated population size within the Point Estero study
area by survey year.





Transects


Mean


Population estimate


Year


sampled


density (S.E.)


(2,508,391 m-)


1965


15


0.1010(0.0316)


253,350


1966


15


0.0995(0.0257)


249,600


1967


25


0.0718(0.0147)


180,100


1970


25


0.0606(0.0116)


152,000


1971


25


0.0166(0.0037)


4 1 ,650


1973


25


0.0103(0.0043)


25.850


1974


25


0.0066(0.0026)


16,550


1978


25


0.0055(0.0017)


13,800


1993


25


0.0072 (0.0026)


18,050



RELATIONSHIP BETWEEN SEA OTTER AND RED ABALONE



49



O

<



13

o
o

Ul



<
m

<



<



15



10-



5-



ii



6.\



«.



O O MEAN COUNT
• • ADJUSTED MEAN



64 69 74



'•••-O

I I I I I I I I I I I I I I I



79



84



89



94



YEAR

Figure 2. Mean red abalone count per transect and mean count adjusted for covariation between
years in distribution of transect depth and substrate type.



O A

O

o

o

o

r: 3-1



2



N
(/I



3

a.
o

Q.



First Year S«a Otters Foraged
within Study Area



'I



-1



T



64



69



74



79



f 1 f I T I



84



89



94



YEAR

Figure 3. Estimates of red abalone population size (95% CI) within the Point Estero study area
through time.



50



CALIFORNIA FISH AND GAME



statistical significance to the temporal and geographic patterns within strata.

The size frequency distribution of red abalone within the Point Estero study area
remained relatively unchanged through 1 978. No abalone were accessible for measuring
in 1993. There were no statistically significant differences in the size frequency
distributions ofmeasured abalone in pairwise comparisons (Kolmogorov-Smimov 2-
sample tests). The mean sizes ofmeasured abalone ranged from a high of 181 mm in
1971 to a low of 155 mm in 1978 (Fig. 5).

There were also no statistically significant temporal trends in the proportion of
abalone within size groups (/; sm = 0.283, P > 0.05; /; med = -0.2 \1,P> 0.05; and /;
Ig = -0.333, P > 0.05). However, the proportion of abalone in the 1993 survey within
the smallest size group (< 1 02 mm ) was higher than on any prior survey and there w ere
proportionally fewer large abalone (> 196 mm).

Reoccupation of the Point Estero region by sea otters occurred through southward
range expansion between 1967 and 1971 (Fig. 1). Sea otters were first observed
foraging within the study area in 1967 (E. Ebert, CDFG, pers. comm.). The range
expanded beyond Point Estero to Cayucos in 1 972. In the interim, the peripheral male




STRATA 5



^-f-



I I I I



I I



STRATA 4



-f-f-



T 1— T



1 — I — I — r I I



STRATA 3



■♦^



I I I I I — I— I — I— r



20
10






I

1



I I



I I I



STRATA 2



• •



1 — I — I ▼ I — r— T-



T — r



I I I



STRATA 1



• ^ •



-I — I — r



I I r I I
60



^-1 — I — 1 I T — I — r— T — I I I — r—r
74 79 84



94



YEAR



Figure 4. Mean red abalone count per transect (S.E.) by strata and survey year. Shaded area
includes surveys with mean counts >10 abalone/transect.



RELATIONSHIP BETWEEN SEA OTTER AND RED ABALONE



51



group actively foraged in the vicinity of the Point Estero study area. There are no direct
measures of changes in foraging pressure within the study area during this time period.

However, aerial counts of sea otters within the southern peripheral portion of the
range between 1968 and 1972 varied considerably (Table 2). The variation in counts
followed a seasonal pattern, with high counts between January and July and relatively
low counts during the remaining months. The highest count each year ranged from 62
in 1968 to 187 in 1971.

Sea otter food habit observations collected within the vicinity of the Point Estero
study area in 1971 and 1972 documented a marked shift to the use of a broad forage
base (Wild and Ames 1974). In 1971, red abalone comprised almost 60 percent by
number of the food items observed being consumed by sea otters. In 1972, that
proportion had declined to less than 2 percent (Fig. 6).

DISCUSSION

The Point Estero surveys documented a precipitous decline in abalone abundance
between 1967 and 1971. This decline coincided with the reoccupation of the area by
sea otters. This coincidence suggests that sea otters could have caused the decline,
particularly since sea otters were actively feeding on abalone through 1 97 1 . However,
abalone populations have also declined in areas outside of the sea otter's range.
Declines in these areas have been attributed to such factors as over-exploitation (Estes
and VanBlaricom 1985) and disease (Haaker et al. 1992).





200




190


?


180


E


170


1—
o

z

LJ


160
150
140


<
LJ

2


130
120




110




100




SURVEY YEAR



Figure 5. Mean red abalone size (S.E.) by survey.



52



CALIFORNIA FISH AND GAME



Table 2. Number of sea otters observed at the southern range periphery by area during aerial
surveys. 1 968 through 1 972. Area I = Cambria to White Rock, Area 2 = White Rock to Cambria
Radar Station. Area 3 = Radar Station to Point Estero, and Area 4 = South of Point Estero.





Total
count




Percent


within




Date


Area 1


Area 2


Area 3


Area 4


8 Nov 68


62


85


13


2





20 Dec 68


34


97


3








3 1 Jan 69


117





98


2





10 Feb 69


100


2


98








10 Mar 69


129


57


43








7 Apr 69


73





23


77





5 May 69


41


5


80


15





2 Jun 69


40


10


80


10





1 Aug 69


59


5


81


14





8 Sep 69


26


58


42








6 Oct 69


43


2


89


9





1 Dec 69


41


2


66


32





7 May 70


165


95








5


17 Sep 70


45


20


78


2





13 Feb 71


60


8


10


82





16 Apr 71


162


4


94


2





1 Jul 71


187


11


58


29


2


5 Oct 7 1


86


6


62


24


8


4 Jan 72


75


5


13


82





19 Apr 72


91


11


6


2


81


"^Study area 1


ocated within


Area 3.









The commercial red abalone fishery had operated continuously within the Point
Estero area since the early 193()'s. Morro Bay was the primary port of landing for red
abalone taken from this area. Landings there remained relatively stable for decades
then decreased rapidly over a short period of time. However, the decline occurred
more slowly than that observed within the Point Estero study area ( Fig. 7 ). Red abalone
resources in the region supported a commercial harvest through 1978. Fishing effort
was gradually concentrated into a smaller area as it shifted southward into less
productive habitat south of Morro Bay. Sea otters expanded their range beyond this
area into the Pismo Beach area in 1978.

Commercial abalone fishing can be excluded as a probable cause for the precipitous
decline in abalone density observed within the Point Estero area for two primary
reasons: I ) the decline occurred across all size classes of abalone, even though the
minimum commercial red abalone size limit is 197-mm. and 2) the decline appears to
have occurred sequentially from north to south in a relatively restricted geographical
area compared to the range of operation typical of the fleet. Furthermore, it is
improbable that a fishery-caused decline would coincide exactly with the reoccupation
of the area by sea otters.



RELATIONSHIP BETWEEN SEA OTTER AND RED ABALONE



53



tr
111
m






ui

a.



60
50
40
30
20
10




S

e

1

a



c



.1 11



o



o

o
a



o
o



8



I



c



^ 1971 (n = 82)
ZZZl 1972 (n = 52)






a lo



I



e

o
a



00

JO



E
u



PREY

Figure 6. Changes in sea otter prey selection in vicinity of Point Estero between 1 971 and 1 972.






o

o.

o
o
o

X

UJ

o

-J

<

09

<

o

UJ




MORRO BAY
COMMERCIAL LANDINGS



80



85



90



YEAR

Figure 7. Commercial red abalone landings at Morro Bay from 1960 through 1992.



54 CALIFORNIA FISH AND GAME

No evidence exists to suggest that illegal take changed appreciabl) during this time
period despite the focused law enforcement effort generated by the controversy. It also
seems probable that abalone densities would have increased in the absence of fishing
pressure (especially after 1970, Fig. 2) if that pressure was the causative agent in the
initial decline. No such population growth has been observed in the two decades
following the collapse of the fishery.

Disease can be excluded as the probable cause for the observed decline because
of a lack of evidence given considerable research diving and commercial activity in
the area. Moreover, abalone were found only in narrow crevice habitat in every survey
conducted after the area was reoccupied by sea otters. It seems improbable that
survivors from a widespread disease would be limited to this microhabitat.

Changes in habitat can also be excluded since analysis demonstrated that appreciable
habitat modifications or sampling biases had not occurred.

The density of red abalone within the Point Estero study area stabilized within a
few years of the initial reoccupation of the area by sea otters (0.007/m-). This density
is similar to the abalone densities reported in several studies conducted within the
long-established sea otter range (Ebert 1968, North 1965) and is low enough to
preclude commercial effort and limit recreational harvest to a few knowledgeable
individuals. Higher abalone densities have been reported within reoccupied habitat,
but. they occurred in particularly crevice-rich habitat (Lowry and Pearse 1 973, Cooper
et al. 1977, Hines and Pearse 1982).

The temporal and geographical pattern of decline in shellfish abundance is
comparable to that reported for Pismo clams when sea otters reoccupied beaches with
clams in Monterey Bay (Miller et al. 1975, Stephenson 1977) and Pismo Beach
(Wendell et al. 1986). The documented loss of shellfish fisheries associated with sea
otter reoccupation strongly suggests the pattern can be used to predict future losses
wherever sea otter range expansion occurs.

MANAGEMENT IMPLICATIONS

This study provides quantitative documentation of large-scale depletion of abalone
stocks directly attributable to the foraging activities of sea otters. This conclusion
supports the view that socioeconomic benefits derived from recreational and commercial
shellfish fisheries that have developed in the absence of .sea otters will largely be lost
through sea otter range expansion.

However, there are also other positive effects associated with sea otter range
expansion. Algal production has been observed to increase in many areas reoccupied
by sea otters due to the reduction in abundance of herbivorous macroinvertebrates
(North 1965, Estes and Palmisano 1974, Duggins 1980). Although evidence is
generally lacking, these increases presumably can, in turn, infiuence the abundance of
finfish populations that are limited by a lack of habitat or forage provided by algae.
Sea otter range expansion also decreases the risks the population faces from human
activities, particularly from large-scale oil spills, and increa.ses the opportunities for
observing sea otters.



RELATIONSHIP BETWEEN SEA OTTER AND RED ABALONE 55

Ongoing debate focuses on the possibility of limiting sea otter distribution while
insuring a secure future for sea otters and providing for human use of shellfish
resources. If both concerns are to be provided for, the reoccupation of the sea otter's
natural range would have to be limited through zonal management.

ACKNOWLEDGMENTS

This study, with a temporal scope covering almost 3 decades, draws upon the
research efforts of a great many individuals. I acknowledge the extensive contributions
made by the previous principle investigators K. Cox ( 1 964), R. Poole ( 1 965), E. Ebert


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