ACTIVITY PATTERNS AND FEEDING CHRONOLOGY OF THE ROCKFISH, ATROVIRENS, IN A CENTRAL CALIFORNIA

A Thesis Presented to The Faculty of the Department of Biology San Jose State University

In Partial Fulfillment · of the Requirements for the Degree Master of Arts

By Gilbert S. Van Dykhuizen May 1983 ABSTRACT

Activity patterns, home range behavior, feeding habits, and chronology of adult kelp rockfish,·, were investigated in a kelp forest in Carmel Bay, California. Kelp rockfish abundance fluctuated with kelp density and canopy cover in this study area. were distributed throughout the water column both day and night in the kelp season and were confined to the bottom in the non-kelp season. Tagged kelp rockfish occupied home ranges throughout the study, although several departed as a result of storms and reduced kelp density. Kelp rockfish fed opportunistically on available and abundant organisms including kelp-associated, open water, and epibenthic prey. Digestive states and rates on fish prey were determined in the laboratory, an~ kelp rockfish fully digested a medium-sized meal of juvenile Sebastes in approximately 33 hours. Initial time of feeding was estimated for field-collected kelp rockfish containing juvenile . From recency of feeding indices, feeding appeared to occur at all times of day with a tendency towards dawn and night feeding.

iii ACKNOWLEDGMENTS

I would like to thank the members of my committee, Drs. Greg Cailliet, Ralph Larson, and Robert-Lea for their helpful comments, support, and assistance during the course of this work. Dr. Mike Foster also provided valuable suggestions along the way. Many thanks and appreciation go to the divers who assisted me, including Todd Anderson, Mickey Singer, Mark Carr, John Heine, Don Canestro, Jim Brennan, Bruce Welden, Alan Fukuyama, Mike Denega, Dave Ebert, Drs. David Schiel and Ralph Larson, Doug Maier, Michelle Whitney, Susan Dearn, Barbara Pierson, and Alistair Hamilton. The Pebble Beach Corporation kindly allowed diving access to Stillwater Cove. Peter Slattery helped identify stomach contents of kelp rockfish. Dr. David Schiel, Dr. Liz Denley, and Kevin Lohman helped with statistical procedures. Kevin Lohman and Lynn McMasters drafted the figures. Deborah Tuel typed the final manuscript. My thanks and appreciation are extended to all these fine people. Thanks also go to Larry Jones, Ken DeLopst, and Preston Watwood for maintaining diving equipment and general assistance. The staff and faculty at Moss Landing Marine Laboratories were also helpful and supportive during my stay at the lab. The use of Moss Landing Marine Laboratories' HP 9825 computer system was an important aid in the completion of this project. Finally, I would like to thank the David and Lucille Packard Foundation for financial assistance in purchasing equipment and supplies.

iv TABLE OF CONTENTS

ABSTRACT iii ACKNOWLEDGMENTS iv LIST OF FIGURES vi LIST OF TABLES vii

INTRODUCTION 1

MATERIALS AND METHODS 4 Study Site 4 Seasonal and Diel Activity 5 Home Range Behavior 8 Feeding Habits and Chronology 9 Digestive States and Rates 10

RESULTS 14 Seasonal ~nd Diel Activity 14 Home Range Behavior 15 Feeding Habits and Chronology 16 Digestive States and Rates 18 DISCUSSION 20

LITERATURE CITED 26

v LIST OF FIGURES

Figure 1 Map showing study area. 32 2 Map of Arrowhead Point. 34 3 Map illustrating transect sampling procedure. 36 4 Flow diagram illustrating the three-factor ANOVA model. 38 5 Cumulative abundance versus number of transects. 40 6a Canopy cover estimates at Arrowhead Point. 42 6b Mean Macrocystis density and percentage of plants with greater or less than five stipes at Arrowhead Point. 42 7 Number of fish per 40 m2 transect in kelp versus non-kelp season. 44 8 Diel activity in kelp versus non-kelp season. 46

9 Mi c ~habitat use in ke 1 p versus non-ke 1 p season. 48 10 Cumulative number of prey types versus number of stomachs. 50 11 Percent number and frequency of occurrence for dawn, noon, dusk, and night collected stomachs. 52 12 Fullness-recency data versus time of collection. 54 13 Estimated initial feeding time of field-collected specimens. 56 LIST OF TABLES

Table

1 Three-factor ANOVA comparing seasons, time of day, and behaviors. 57 2 Three-factor ANOVA comparing seasons, time of day, and microhabitat. 58

3 Home range observatons for 14 tagged kelp rockfish. 59 4 State of digestion indices. 61 INTRODUCTION

The subtidal kelp environment of the central California coast supports a variety of fishes, the ~ost numerous in abundance and biomass being the rockfishes (: Sebastes). Rockfishes are also a major constituent of sport and commercial fisheries along California and the eastern north Pacific coast. Rockfishes have been included in many investigations of kelp forest fishes in southern California (Larson, 1972; Burge and Schultz, 1973; Feder et al., 1974; Ebeling and Bray, 1976; Hobson and Chess, 1976; Coyer, 1979; Ebeling et al., 1980; Ebeling et al., 1980; Larson, 1980; Love, 1980; Hobson et al., 1981). Studies in central California have dealt with the spatial partitioning and food habits of rockfishes (Miller and Geibel, 1973; Hallacher, 1977; Roberts, 1979; Love and Westfall, 1981). Of these investigations few have focused on the behavior and ecology of a single (Love, 1980; Larson, 1980). Concentrating on a single species often leads to a more detailed understanding of an organism's role in its environment. In addition, the effects of seasonal and diel variation in diet and habitat can ultimately provide insight into the growth and reproduction of a species. This information will also help in assessing the status of local populations of a species with respect to fishing pressure by divers and fishermen. One of the more common kelp forest rockfishes is the kelp rockfish, Sebastes atrovirens, which has· been studied in both central and southern 2

California (Larson, 1972; Ebeling and Bray, 1976; Hobson and Chess, 1976; Hallacher, 1977; Roberts, 1979). The kelp rockfish ranges from Punta San Pablo, Baja California, to Timber Cove, California and is found primarily in kelp forests to· depths of 45 meters (Miller and Lea, 1972). The adults reach a reported maximum length of 425 mm (Miller and Lea, 1972). Juveniles of this species recruit to the kelp canopy in late summer in central California (Singer, 1982; Carr, 1983). Adults are found throughout the water column and feed on kelp-associated invertebrates and juvenile fishes (Larson, 1972; Roberts, 1979). Hobson and Chess (1976) observed kelp rockfish to feed nocturnally and usually idle near the bottom during daylight hours. Rockfishes are known to maintain home ranges and defend territories. Carlson and Haight (1972) showed , 2· flavidus, to h~ve a home range and also return to this home range from as far away as 22.5 km. Larson (1980) found the , 2· carnatus, and the black and yellow rockfish, 2· chrysomelas, two species segregated by depth, to defend territories. Information concerning the home range or territorial behavior of the kelp rockfish is lacking. Since the activity and feeding habits of a species may change over its geographic range (Fox and Morrow, 1981), the purpose of this investigation was to observe the activity patterns and feeding chronology of the kelp rockfish and compare these findings with those found for southern California kelp rockfish. 3

The major questions addressed were: 1) Are there seasonal abundance and activity patterns, and what factors contribute to changes in these patterns? 2) Do kelp rockfish maintain" a home range or a territory similar to other rockfish species? 3) What are feeding habits and feeding chronology of the kelp rockfish in central California and how do they differ from individuals of this species in southern California? 4

MATERIALS AND METHODS

Study Site

This study was conducted in ~acrocystis pyrifera kelp habitat off Arrowhead Point in Stillwater Cove, Carmel Bay, California (36°33'30"N, 121°55'30''W) (Figs. 1, 2). Stillwater Cove is protected from northwesterly swell conditions but is exposed to severe southerly storms which commonly occur from October through February. During the summer months, June through September, M. pyrifera forms a thick canopy which, along with many of the kelp plants, is removed during the winter storms.

In addition to~· pyrifera, there are uncommon occurrences of other such as Pterygophera californica, Cystoseira osmundacea, and spp. The botto~ topography consists of large granitic boulders and vertical rock outcroppings extending approximately 4 m above the sea floor. Sand channels are interspersed among the boulders and outcroppings. The depth at the study site varies from 9 m at the large outcrops to 12.5 m, MLLW, on the sea floor. The reef substrate is encrusted with various erect and crustose sponges, tunicates, and bryozoans as well as a thick mat of red articulating coralline algae (Foster, 1982).

~· pyrifera canopy cover and density were measured over the year to determine the fluctuation of this habitat. ~· pyrifera density was estimated by running three 20m-long by 1m-wide transects during six 5

different sampling dates over the year. Both the number of plants per m2 and number of stipes per plant were counted. Percent canopy cover in the study area was estimated on a scale of 1 to 4 with: 1 = 0-25%; 2 =

25-50%; 3 = 50-75%; 4 = 75-100%.

Seasonal and Diel Activity Seasonal and diel activities were observed in depth-stratified transects made day and night over the course of 17 months. Three buoys were anchored by pitons in rocks along the kelp forest-sand channel border. Concrete nails with numbered strips of bicycle handlebar tape were placed at one meter intervals along the bottom of the 40 m by 20 m study area (Fig. 3). For sampling, a meter tape was stretched between the three buoys, and random numbers were chosen between 0 and 40 to determine the starting points for transects. Random numbers were selected four or more meters apart to avoid overlapping transects. Another transect tape was extended by swimming into the kelp forest at a 50-degree angle north for a distance of 20 m. Kelp rockfish were visually counted along a 20m-long by 2m-wide transect. One meter on each side of the transect tape was surveyed at the canopy, mid-water (6.5 m), and on the bottom. These three zones were inspected in order of increasing depth to minimize the disturbance of kelp rockfish. Five transects at each zone were surveyed for a combined total of 30 transects for each day and night sample. Day and night transects were made within 24 hours of each other. Two day-night samples (i.e., 60 6

transects) were attempted for each month of the study. During night dives kelp rockfish reacted to dive lights by slowly moving away from the light beam. Temperature, horizontal visibility, surge, and weather conditions were recorded before each sampling period. Temperatures were measured to the nearest 0.1°C at the surface, mid-water, and bottom. Horizontal visibility was estimated to the nearest meter using a white 24 em disk attached to a transect tape. The visibility was recorded as the distance at which the disk disappeared. Surge, or the lateral movement of water, was qualitatively determined as low (0-1 m), medium (1.5-2.0 m), and heavy (2.5 m or greater). Weather conditions noted were cloud cover, wind direction, and swell height. Once an adult kelp rockfish (>160 mm) was encountered along the transect, the'activity and microhabitat association were recorded. Four different activity modes were distinguished for kelp rockfish. "Hovering" was defined as hanging motionless in the water column with only slight fin movement. "Hovering-swimming" activity occurred when kelp rockfish maintained a position in the water column by swimming against a current or surge. "Swimming" was noted as active locomotion by the kelp rockfish. "Resting" was defined when a kelp rockfish was in contact with the substratum. Three microhabitats were designated: kelp, rock, and shelter. Kelp included stipes or canopy while rock included high and low relief rock. Shelter holes included cavities within rocks. 7

The numbers of kelp rockfish per transect for 55 transects were plotted in a frequency histogram by season. Seasonal counts were compared with a Mann Whitney U Test with tied ranks analysis. The Z statistic was calculated due to the large sample size (Zar, 1974). The activity data were analyzed using a three factor ANOVA with replication (Fig. 4) (Sakal and Rohlf, 1969). Factors such as vertical distribution and activity were sorted out and tested for differences; cells contained two replicates each. Data were transformed by adding one and taking the natural log. Cochran's test was used to test the variances (Winer, 1971). Due to unequal numbers of transects between seasons the number of transects was randomly standardized to 55 for each zone within each season. Cumulative mean abundances compared to number of transects indicated this'sample size was sufficient (Fig. 5). A three-factor ANOVA with replication was used to compare variation in abundance among season, time of day, and microhabitat. These data were obtained from day and night transects and standardized to have equal replication within cells. Cells contained two replicates each randomly chosen from the transects in that category. Data were also transformed by adding one and taking the natural log. Homogeneity of variances was tested using Cochran's test. 8

Home Range Behavior A tagging study was conducted from September 1981 to December 1982 at Arrowhead Point. Kelp rockfish were captured using a 1 x 1 x 1.5 m opening/closing diver-held net witn 3 mm nylon stretch mesh on a 1.3 em PVC frame mouth. Each captured fish was tagged with a Floy FD-67 anchor tag, made of vinyl plastic, inserted into the dorsal musculature; lengths and weights were not taken. Tags were color- and numerically-coded so that individual kelp rockfish could be distinguished underwater or reported if captured. The locations of tagged fish were monitored in a 40 m x 20 m area. The bottom in this site was divided into fifty 4 x 4 m squares marked with orange surveyor's tape. Details of the bottom topography were diagrammed on underwater paper so that the location and microhabitat of tagged kelp rockfish could be noted within each quadrat. Observations of tagged kelp rockfish commenced approximately two weeks after tagging. Two methods were used in resighting tagged kelp rockfish. Tagged fish were haphazardly observed while doing day and night transects. Approximately 34 dives during the course of the study were devoted to searching the entire study area for tagged individuals. For each tagged kelp rockfish the horizontal location, vertical zone, activity, and microhabitat association were recorded. Home range was defined in this study as the area in which an individual lives (Brown and Orians, 1970). The home site was defined as the particular quadrat in which the tagged fish was repeatedly observed. 9

The home range was noted as the distance from a particular quadrat or specific habitat as falling into one of three categories: 1) 0-3 m; 2) 3.5 -6.5 m; 3) 7.0-10.5 m.

Feeding Habits and Chronology Approximately 118 adult kelp rockfish (>160 mm) were speared as samples for gut contents. All fish were collected in the kelp forests of Carmel Bay between June and November 1982. Collections were made at dawn (1-2 hours following first light), midday (1200-1300 hours), dusk (during and just after sunset), and at night (four or more hours following last light). Speared fish were placed in a mesh collecting bag underwater and thereafter placed on ice to slow digestion. Standard length, total length, and sex were recorded for each specimen. The '"gut was removed, fixed in 10% formalin, and preserved in 70% ethanol. Fullness and digestive state of the stomach contents were subjectively estimated. Fullness was estimated based on size and distention of the stomach on a scale of 1 to 4: 1 = empty; 2 = trace - 1/3 full; 3 = 2/3 full; and 4 =full. The relative volume of stomach contents was not measured. Digestive states of stomach contents were categorized by a visual index of recognizability based upon laboratory digestive state experiments. Prey in the stomachs were identified to species where possible or separated into general taxonomic categories (e.g., amphipods, mysids, , etc.). Prey items were counted and the percent by number (%N) 10

and percent frequency of occurrence (%F.O.) were calculated for each prey category. The numerical importance and frequency of occurrence (that proportion of stomachs containing a specific prey item) reflect the process of selection used by the fish in its feeding behavior by pointing out how many prey and how often a certain type of prey was selected (Cailliet, 1976). Eleven prey categories were determined and were separated by time of collection (i.e., dawn, noon, dusk, night) to show which prey were important during which period. A plot of cumulative number of prey types against number of stomachs was constructed for each period of collection to assess the adequacy of sample sizes. The point at which this curve levels off is an indication that a sufficient number of samples have been taken to adequately characterize the array of prey types eaten by a species (Hurtubia, 1973).

Digestive States and Rates Various investigators have emphasized that in order to adequately assess fish feeding chronology, it is important to know the digestive rates of the f1sh studied (Bajkov, 1935; Darnell and Meierotto, 1962; Jenkins and Green, 1977; Swenson and Smith, 1977). Since kelp rockfish consume both vertebrate and invertebrate prey, differential digestion rates may occur (Windell, 1972; Macdonald et al., 1982). Experiments were designed to determine digestive rates of two important prey items, juvenile rockfishes and the kelp isopod, Idotea 11

resecata. Unfortunately, it was not possible to determine the digestive rate of Idotea since kelp rockfish would not eat isopods in the laboratory environment. Kelp rockfish were captured buth by hook-and-line and using the diver-operated opening/closing nylon mesh net. When kelp rockfish had over-inflated swimbladders, a hypodermic needle was inserted behind the pectoral fin into the swimbladder to expel the gases. All kelp rockfish used for this experiment were collected at Stillwater Cove. Solitary individuals were held in ten gallon aquaria supplied with running sea water. The aquaria were stationed in a sheltered outdoor location exposed to normal day and night light cycles. Kelp rockfish were acclimated for a period of two to three weeks prior to the experiment. Daily or every other day fish were fed a diet consisting of iive Sebastes juveniles or live , Spirinchus starksi. Sebastes juveniles were collected using the previously mentioned diver-operated net. Night smelt were captured at Bennett. Slough in Moss Landing using a small beach seine. Prior to the experiment kelp rockfish were fasted for two to three days, as recommended by Windell (1978). Various techniques have been used in determining digestive rates, evacuation rates, and daily rations of fishes. These techniques include x-radiography (Edwards, 1971), radioisotope marking of food (Kolehaimen, 1974; Peters and Hoss, 1974; Fitzgerald and Keenlyside, 1978); dye marking of food (Lane and Jackson, 1969); serial sacrifice (Bajkov, 12

1935; Webster, 1942; Pandian, 1967; Keast and Welsh, 1968; Magnuson, 1969; Tyler, 1970; Brett and Higgs, 1970; Macdonald et al., 1982), and use of emetics or stomach flushing (Seaburg and Moyle, 1964; Jernejcic, 1969). Initially, the emetic (tartaric acid) recommended by Jernejcic (1969), was administered to several kelp rockfish. This emetic failed to induce vomiting in kelp rockfish, hence the serial sacrifice method was used. Each adult kelp rockfish was given a standard meal size by weight consisting of live juvenile Sebastes. The rockfish juveniles were consumed within one half hour after being placed in the aquarium. One kelp rockfish was sacrificed 3, 6, 9, 12, 18, 24, 27, 30, and 33 hours after feeding. Standard length, total length, and sex were recorded. The digestive tract was removed, fixed in 10% formalin, and preserved in 70% ethanol. To evaluate the digestive state of the prey, a visual index of recognizability was constructed similar to that proposed for by Karpov and Cailliet (1978). This method involved a description of various body parts over time. The indices of digestion and fullness were combined in a 2 x 2 matrix (Karpov and Cailliet, 1978) in which the major feeding states were : A= not recently eaten or full (fullness states 1 and 2 vs. digestive states 3 and 4); B = recent but not full (fullness states 1 and 2 vs. digestive states 1 and 2); C =recent and full (fullness states 3 and 4 vs. digestive states 1 and 2); and D = 13

full but not recently eaten (fullness states 3 and 4 vs. digestive states 3 and 4). Fullness-recency histograms were plotted for each of the period kelp rockfish were sampled in the field. Fullness-recency data for all four periods of capt~re were compared using a chi-square contingency table analysis (Zar, 1974). Dawn and night samples were combined, and noon and dusk samples were combined to compare with the full recent categories. The categories of not full-recent and full-recent were combined and compared to not full-not recent and full-not recent. Digestive rates were also estimated from laboratory experiments. The difference in weights of the juvenile Sebastes before and after feeding were recorded, and the percent digestion per hour and number of grams digested per hour were calculated. Field collected specimens containing juvenile fishes in their stomachs were examined to estimate the initial time of feeding. The initial feeding times were estimated using the digestive state indices and rates of digestion of juvenile Sebastes from laboratory experiments. 14

RESULTS

Seasonal and Diel Activity

The~- pyrifera canopy cover and density estimates indicated that there were two distinct seasons. The kelp season, typically from June to September or October, was characterized by a dense canopy (Fig. 6a), formed by kelp plants with more than five stipes (Fig. 6b). The non-kelp season ranged from October to April or May and was characterized by a sparse canopy (Fig. 6a). Severe winter storms occurred during this time resulting in a removal of canopy and the supporting plants. As storms subsided in spring, high densities of newly recruited~- pyrifera appeared (Fig. 6b) followed by the formation of a dense canopy in the summer months. As the canopy cover and kelp densities changes, so did the density, activity patterns, and microhabitat association of the kelp rockfish. In the bottom zone, numbers of kelp rockfish per 40 m2 transect were significantly higher during the kelp season than in the non-kelp season

(Mann-Whitney U test, with Z statistic; p <.05; Fig. 7). ~1ultiple numbers of fish per transect occurred more often in the kelp season. Kelp rockfish were distributed throughout the water column during both day and night in the kelp season (Fig. 8). Kelp rockfish primarily hovered above the bottom during the day and night although some individuals were observed resting. During the non-kelp season, kelp rockfish were only in the bottom zone. They mainly hovered above the 15

bottom during the day and rested at night (Fig. 8). Although kelp rockfish were observed swimming about, the majority were stationary, either hovering or resting. A three-factor ANOVA indicated significant differences between seasons with respect to vertical distribution and between day and night (Table 1). Interestingly, there was no significant difference between day and night behavior within a season. Results of this three-factor ANOVA are difficult to interpret because the high order interaction is significant. In this situation single order interactions (i.e., season vs. time of day) cannot be separated. The changes in activity patterns are supported by differences in microhabitat utilization between seasons (Fig. 9). Kelp rockfish strongly associated with kelp during day and night within the kelp season. Kelp"rockfish associated with both kelp and rock during the day, but primarily with rock at night during the non-kelp season. These differences were significant by way of a three-factor ANOVA comparing season, time of day, and microhabitats (Table 2).

Home Range Behavior A total of fourteen kelp rockfish were tagged, five on 22 September 1981 and nine on 19 November 1981. Some of the tagged kelp rockfish were sighted repeatedly for periods over a year after tagging, while others were resighted only infrequently. Of those resighted frequently, most observations were within 3 m of their home site, indicating some 16

tendency to limit activities to a small home range (Table 3). Four of the fourteen tagged fish were observed consistently (Table 3). Of these four, two occurred within three meters of their home site in 90% of the observations. The other two were tesighted 67-70% of the time within 3 m of their home site. Kelp rockfish were seldom observed more than 6.5 m from their home site. Several tagged kelp rockfish were observed in 1981 but were not resighted in 1982 (Table 3). The typical home site contained a shelter hole surrounded with M. pyrifera plants. Kelp rockfish typically hovered above the bottom where the home site was located. Several tagged individuals were observed hovering in the mid-water zone above the home range. A large shelter hole within a home range usually contained four to five kelp rockfish. Many of the shelter holes were occupied by gopher and copper rockfishes

(~. caurinus). These two species often chased kelp rockfish out of the shelter hole, but the kelp rockfish returned within a few minutes. Kelp rockfish often took refuge in shelter holes when repeatedly disturbed by divers.

Feeding Habits and Chronology A total of 118 kelp rockfish were sampled and examined during the kelp season in an effort to determine feeding chronology. The cumulative prey type curves versus the numbers of stomachs examined showed that the dawn and dusk sample sizes were adequate (Fig. 10). The curves began to level off for the stomachs collected at noon and at 17

night at about the same number of prey types (8) as dawn and dusk samples. Kelp rockfish fed on a wide size range of prey that included planktonic invertebrates, epibenth1c invertebrates, and juvenile fishes (Fig. 11). The most common prey taken were amphipods, mysids, isopods, , crabs, and juvenile fishes. Rare prey included Doliolium, a pelagic tunicate, and squid. These prey items were present in stomachs from one collection date only. In the case of Doliolium, approximately 20 kelp rockfish were sampled at that time with the majority containing this tunicate. When feeding habits were analyzed with respect to time of day, the opportunistic feeding nature of the kelp rockfish was evident based on the prey items present at different times of the day (Fig. 11).

,· Amphipods and the isopod Dynamenella were important numerically, whereas amphipods, shrimp, and Dynamenella were more frequently found in the stomachs collected at dawn (Fig. 11). Amphipods, mysids, and squid represented the important prey categories both numerically and in frequency of occurrence in stomachs collected at noon. The pelagic tunicate Doliolium was by far the most numerically important prey in the dusk samples but represented only one collection date. Several prey types, including mysids, Dynamenella, juvenile Sebastes, and pelagic tunicates, were frequently found at dusk. Amphipods and Dynamenell a were both abundant and frequent in the stomachs collected at night. 18

~1ysids, Idotea, shrimp, and juvenile midshipmen, , also frequently occurred in the night samples. Mean fullness and recency data indicated that kelp rockfish fed whenever food was available (Fig. '12). Full stomachs occurred at all times of the day, but empty stomachs were most frequent at noon and at dusk. Chi-square analysis indicated that fullness and digestion histograms differed among times of day with kelp rockfish feeding primarily at dawn and at night (p < 0.05). Kelp rockfish must also feed during the day and at dusk when prey such as juvenile Sebastes and plankton transported into the kelp forest are available.

Digestive States and Rates Digestive state indices were constructed from nine serially sacrificed kelp rockfish. The sea water temperature in the aquaria during the digestive rate experiment was 13.5°C, Meals consisted of two juvenile Sebastes with meal weights ranging from 13.4 to 16.5 grams and having a mean of 14.5 grams. The mean weight of the adults was 910 grams (plus or minus 62 grams). Each kelp rockfish consumed approximately 1.6% of its body weight per experiment. Juvenile Sebastes were still recognizable after 12 hours of digestion with most body parts intact (Table 4). The head and body tissues began digesting between 13 and 24 hours, and after 25 hours only cylindrical lumps of tissue surrounding the vertebrae remained. 19

Approximately 0.5 g of the juvenile Sebastes were digested per hour. At this rate it took kelp rockfish about 33 hours to pass the two juvenile Sebastes through the stomach. Using the digestive indices and digestive rate (0.5 g/hr), the intitial feeding time of field-collected kelp rockfish containing juvenile fish was estimated (Fig. 13). Generally, it appears kelp rockfish consumed juvenile fishes during all times of day, as previously shown by the fullness recency data. 20

DISCUSSION

The activity pattern of the kelp rockfish in central California appears to be integrated with the ~nnual cycle of~· pyrifera abundance. Kelp rockfish were distributed throughout the water column during both day and night in the kelp season (June to October) .. In the non-kelp season, kelp rockfish generally hovered over the bottom during the day and were inactive, resting on the bottom at night. Although kelp rockfish were rare in their transects, Ebeling and Bray (1976) found this species to be active (i.e., hovering) both day and night on a reef off Santa Barbara. Hobson and Chess (1976) observed kelp rockfish to rest on the bottom during the day, becoming active in the water column at night at Santa Catalina Island in southern California. There are differences between day and night activity patterns in central versus southern California, but the behaviors observed (i.e., hovering, etc.) are identical. The differences in activity patterns may be attributed to the predictable removal or decrease in size of kelp forests each winter in central California. Densities of kelp rockfish within the study site were significantly lower in the non-kelp season, when storms and the reduction of kelp probably caused this decrease in abundance. Hallacher (1977) and Coyer (1979) mentioned the absence of kelp rockfish in areas lacking high kelp densities and canopy cover. Miller and Geibel (1973) and Carlson and Barr (1977) suggested that nearshore rockfishes may migrate to calmer 21

offshore waters in the winter. ,~- mystinus, tended to seek more protected kelp forests during harsh winter periods (Miller and Geibel, 1973). Kelp rockfish probably seek out protected areas during winter storms. Tagging and telemetry studies could shed light on this question. Numbers of kelp rockfish during the nighttime versus daytime transects were consistently lower. Two possible explanations may account for this difference. First, fish are difficult to see at night, and their abundances may be underestimated. Second, fish are easily disturbed by dive lights. In addition, the numbers of kelp rockfish per cumulative transects were consistent, indicating that they were adequately sampled using this method. Kelp rockfish maintained home ranges throughout much of the year, but often departed once winter storms occurred. Shelter holes represented the base of the home range, providing a refuge from predators and storms. It is possible kelp rockfish forage away from their home range if prey are available in nearby areas. Several factors may explain the disappearance of tagged kelp rockfish. Kelp rockfish could have been preyed upon by predators such as harbor seals, sea lions, or ling . Natural mortality or mortality as a result of tagging may also have occurred. Emigration to calmer, less-disturbed waters is probably the main factor causing the departure as well the reduction of kelp habitat. 22

Unlike kelp rockfish, demersal rockfishes,~- carnatus and S. chrysomelas maintain and defend territories (Larson, 1980). Kelp rockfish co-occur with these two species but do not defend a home site.

The possibility for increased intera~tion between these three species could occur in the non-kelp season. Once kelp is removed by storms and kelp rockfish are limited to the bottom zone, aggressive interactions could occur more frequently. Generally, kelp rockfish appear to feed opportunistically, relying on abundant and available prey during the kelp season. Both this study and that of Roberst (1979) study support opportunism in kelp rockfish feeding habits. Pelagic tunicates, squid, fish larvae, and megalopae are examples of rare prey eaten by kelp rockfish. Thus, kelp rockfish feed on a variety of prey common in kelp forests but commonly eat rare prey wh'en available. Feeding habits data collected by Roberts (1979) during the non-kelp season were used for comparing seasons. During the non-kelp season the feeding habits of the kelp rockfish changed (Roberts, 1979). Since much of the kelp is removed by storms, kelp-associated invertebrates and juvenile fishes must decline in abundance. The primary prey eaten by the kelp rockfish in the non-kelp season were gammarid amphipods, isopods, and brachyurans (Roberts, 1979). Roberts (1979) also noted that approximately 70% of the kelp rockfish stomachs were empty at this time. Concurrently, a peak in fat abundance occurred during and just before the non-kelp season (Roberts, 1979). This suggests that kelp 23

rockfish may rely on fat stores if prey are not available or if sotrms interfere with feeding behavior. The types and activities of prey are often related to the feeding time of a fish species (Starck and· Davis, 1966; Hobson and Chess, 1976). Feeding in kelp rockfish was concentrated during dawn and night, but full stomachs occurred during noon and dusk as well. Zooplankton samples taken in the same study area indicated that large planktonic organisms such as amphipods and mysids are present both day and night in the water column (Singer, 1982). Hobson and Chess (1976) and Hammer (1981) found amphipods, mysids, and sphaeromatid isopods to be primarily active at night in southern California. Juvenile Sebastes are known to be predominantly diurnal in activity (Singer, 1982), whereas juvenile midshipmen, Porichthys are nocturnally active (Quast, 1968). Idotea, the kelp isopod, occurred abundantly during the kelp season and was active both day and night. Dynamenella, a sphaeromatid isopod, is a member of a nocturnally active group of isopods (Hobson and Chess, 1976). This evidence strongly suggests that kelp rockfish feed at all times of the day since prey are available at all times of the day. Rare prey are eaten when present, whereas common prey items might be ignored during influxes of abundant rare prey. The feeding chronology of kelp rockfish apparently differs between central and southern California. From a fairly small sample size only taken at night, Hobson and Chess (1976), concluded kelp rockfish feed at night. Their diet consists primarily of small which inhabit 24

the water column (Larson, 1972; Coyer, 1979; Hobson and Chess, 1976). Quast (1968) found kelp rockfish to utilize all available prey in the kelp forest. Although the diet of kelp rockfish is similar between central and southern Califonria, fhere are differences in chronology. In assessing feeding chronology, it was important to determine the digestibility of the prey items eaten. Digestion rates can vary depending on the types of prey consumed. Gastric evacuation rates were slow for a medium-sized meal of Sebastes juveniles, suggesting that evacuation may take several days if a large number of juvenile rockfishes were eaten. Kariya (196g) observed that , a Japanese rockfish took 70 hours to digest a full meal of chopped meat at 14°C. Crustaceans are known to pass through the stomach at a faster rate (Karpevitch and Kakoff, 1935; Macdonald et al., 1982). , Gadus morhua, completely digested amphipods in approximately twenty hours as compared to bivalves which took over 30 hours to digest (Macdonald et al., 1982). Although the digestibility of prey is important, various factors such as meal size and fish size are also known to influence gastric digestive rates. Gastric digestive rate increased with fish size but was lowered by increased meal size in walleye, a freshwater fish, and (Swenson and Smith, 1973 and Gwyther and Grove, 1981). Kelp rockfish may retain fish in the stomach through several meals of crustaceans depending on the meal size. 25

The availability of prey could affect food consumption rates in kelp rockfish. Food is readily available during the kelp season but possibly declines during the non-kelp season. This would explain the peak fat values during the non-kelp season and the large number of empty stomachs found by Roberts (1979). Food consumption has been shown to change with prey availability in fresh water fishes. Swenson and Smith (1973) found walleye to have higher consumption rates when food was most available during the year. Water temperatures also influence digestive rates. Digestion rates are slower at low temperatures and increase at higher temperatures (Gwyther and Grove, 1981; Brett and Higgs, 1970). During upwelling, low temperatures occur which could affect the kelp rockfish digestive rates and thus potentially influence frequency of feeding. Kelp rockfish are obviously well adapted to live in the kelp forest environment. They are dependent on kelp as a habitat in which to live and on kelp associated as a food source. Feeding habits of the kelp rockfish are similar between central and southern California, whereas feeding chronology appears to differ. The predictable winter removal of kelp apparently influences the distribution, abundance, home range, behavior, and feeding habits of the kelp rockfish in central California. 26

LITERATURE CITED

Bajkov, A. D. 1935. How to estimate the daily food consumption of fish under natural conditions. Trans. Amer. Fish. Soc. 65:288-289. Bray, R. N. and A. W. Ebeling. 1974. Food, activity, and habitat of three picker type microcarnivorous fishes in the kelp forests off Santa Barbara, California. Fish. Bull. 73(4):815-829. Brett, J. R. and Da. A. Higgs. 1970. Effect of temperature on the rate of gastric digestion in fingerling sockeye Oncorhynchus nerka. J. Fish. Res. Bd. Can. 27(10):1767-1779. Brown, J. L. and G. H. Orians. 1970. Spacing patterns in mobile animals. Ann. Rev. Ecol. Syst. (1):239-267. Burge, R. T. and S. A. Schultz. 1973. The marine environment in the vicinity of Diablo Cove with special reference to and bony fishes. Calif. Dept. Fish. and Game. Marine Resources Technical Report 19:433 p. Cailliet, G. M. 1976. Several approaches to the feeding ecology of fishes: pages 1-13 in C. A. Simenstad and S. J. Lipovsky (eds.). Fish food habits studies. First Pacific Northwest Technical Workshop proc. WSG-W077 -22. Carlson, H. R. and L. Barr. 1977. Seasonal changes in spatial distribution and activity of two species of Pacific rockfishes, Sebastes flavidus and S. ciliatus in Lynn Canal, Southeastern Alaska. Mar. Fish. Rev. 1242:23-24. Carlson, H. R. and R. E. Haight. 1972. Evidence for home site and homing of adult yellowtail rockfish, Sebastes flavidus. J. Fish. Res. Bd. Can. 29(7):189-212. Carr, M. H. 1983. Distribution and abundance of juvenile rockfishes (Sebastes) in a central California kelp forest. M.A. Thesis, San Francisco State University. Coyer, J. A. 1979. The invertebrate assemblage associated with and its utilization as a food source by kelp forest fishes. Ph.D. Dissertation, University of Southern California. 364 p. Darnell, R. M. and R. R. Meierotto. 1962. Determination of feeding chronology in fishes. Trans. Amer. Fish. Soc. 91:313-320. 27

Ebeling, A. H. and R. N. Bray. 1976. Day vs. night activity of reef fishes in a kelp forest off Santa Barbara, California. Fish. Bull. 74( 4): 703-717. Ebeling, A. H., R. J. Larson, H. S. Alevizon, and R. N. Bray. 1980. Annual variability of reef-fish assemblages in kelp forests off Santa Barbara, Califonria. Fish. Bull. 78(21):361-377. Ebeling, A. H., R. J. Larson, and H. S. Alevizon. 1980. Habitat groups and island-mainland distribution of kelp-bed fishes off Santa Barbara, Califonria. Pages 404-431 in D. M. Power (ed.). Multidisciplinary symposium on the California islands. Santa Barbara Mus. Nat. Hist. Edwards, D. J. 1971. Effect of temperature on rate of passage of food through the alimentary canal of plaice Pleuronectes platesa. J. Fish. Biol. 3:433-439. Feder, H. M., C. H. Turner, and C. Limbaugh. 1974. Observations on fishes associated with kelp beds in southern Califonria. Cal. Fish and Game, Fish Bull. 160, 144 p. Fitzgerald, G. J. and M. H. A. Keenleyside. 1978. Technique for tagging small fish with I(131) for evaluation of predator-prey relationships. J. Fish. Res. Bd. Can. 35(1):143-145. Foster, M. S. 1982. The regulation of macroalgal associations in kelp forests. Pages 185-205 in L. Srivastava (ed.). Synthetic and degradative processes inrnarine macrophytes. Halter de Gruyter and Co., New York. Fox, L. R. and P. A. Morrow. 1981. Specialization: Species property or local phenomenon? Science 4484:887-893. Gwyther, D. and D. J. Grove. 1981. Gastric emptying in Limanda limanda (L.) and the return of appetite. J. Fish. Biol. 18(3) :245-259. Hallacher, L. E. 1977. Patterns of space and food use by inshore rockfishes (Scorpaenidae:Sebastes) of Carmel Bay, California. Ph.D. Dissertation, Univ. of Calif., Berkeley, 115 p. Hammer, R. C. 1981. Day-night differences in the emergence of demersal zooplankton from a sand substrate in a kelp forest. Mar. Biol. 62:275-280. Hobson, E. S. and J. R. Chess. 1976. Trophic interactions among fishes and zooplankters nearshore at Santa Catalina Island, California. Fish. Bull. 74(3):567-598. 28

Hobson, E. S., W. N. McFarland, and J. R. Chess. 1981. Crepuscular and nocturnal activities of California nearshore fishes, with consideration of their scotopic visual pigments and the photic environment. Fish. Bull. 79(1):1-30. Hurtubia, J. 1973. Trophic diversity measurement in sympatric predatory species. Ecology 5~:885-890. Jenkins, B. W. and J. M. Green. 1977. A critique of field methodology for determining fish feeding periodicity. Env. Biol. Fish. 1(2) :209-214. Jernejcic, F. 1969. Use of emetics to collect stomach contents of walleye and largemouth bass. Trans. Amer. Fish. Soc. 98(4):698-702. Kariya, T.a 1969. The relationship of food intake to the amount of stomach contents in Mebaru, Sebastes inermis. Bull. Jap. Soc. Sci. Fish. 35(6):533-535. Karpevitch, A. and E. Bakoff. 1935. The rate of digestion in marine fishes. Zool. Zhur. 16:28-44. Karpov, K. A. and G. M. Cailliet. 1978. Feeding dynamics of Loligo opalescens j1!_ C. W. Reckseik and H. W. Frey (eds.). Biological, oceanographic, and acoustic aspects of the market squid, Loligo opalescens Berry. Calif. Dept. Fish and Game 169:45-65. Keast, A. and L. Welsh. 1968. Daily feeding periodicities and food uptake rates and dietary changes with hour of day in some lake fishes. J. Fish. Res. Bd. Can. 25(6):1133-1144. Kolehaimen, S. E. 1973. Daily feeding rates of bluegill (Lepomis macrochirus) determined by a refined isotope method. J. Fish. Res. Bd. Can. 31:61-74. Lane, T. H. and H. M. Jackson. 1969. Voidance time for 23 species of fish. USDOI Inv. in Fish Control 33, 9 p. Larson, R. J. 1972. The food habits of four kelp bed rockfishes (Scorpaenidae:Sebastes) off Santa Barbara, California. M.S. Thesis, Univ. of Calif., Santa Barbara. Larson, R. J. 1980. Competition, habitat selection, and bathymetric segregation of two rockfish (Sebastes) species. Eco l. Monogr. 50(2) :221-239. 29

Love, M. S. 1980. Isolation of olive rockfish, populations of southern Califonria. Fish. Bull. 77(4):975-983. Love, M. S. and M. V. Westfall. 1981. Growth, reproduction, and food habits of olive rockfish, Sebastes serranoides off central California. Fish. Bull. 79(3) :533-546. MacDonald, J. S., K. G. Waiwood, and R. H. Green. 1982. Rates of digestion of different prey in Atlantic cod (Gadus morhua), Ocean Pout (Macrozoarces americanus), Winter Flounder (Pseudo leuronectes americanus), and American Plaice (Hippoglossoides platessoides . J. Fish. Res. Bd. Can. 39(5):651-659. Magnuson, J. J. 1969. Digestion and food consumption by skipjack (Katsuwonus pelamis). Trans. Amer. Fish. Soc. 98(3):379-392. Miller, D. J. and J. J. Geibel. 1973. Sumnary of blue rockfish and life histories; a reef ecology study; and giant kelp, M. pyrifera experiments in Monterey Bay, California. Cal. Fish and Game, Bull. 158:1-137. Miller, D. J. and R. N. Lea. 1972. Guide to the coastal marine fishes of California. Cal. Fish and Game, Bull. 157:1-249. Pandian, T. J. 1967. Intake, digestions, absorption, and conversion of food in fishes, Megalops cyprinoides and Ophiocephalus striatus. Mar. Bio. 1(1):16-32. Peters, D. S. and D. E. Hess. 1974. A radioisotope method for measuring food evacuation time in fish. Trans. Amer. Fish. Soc. 103( 3): 626-629. Quast, J. C. 1968a. Fish fauna of the rocky inshore zone. Pages 35-79 in North, W. J. and C. L. Hubbs (eds. ). Utilization of kelp bed resources in sourthern California. Cal. Fish. and Game Bull. 139:35-79. Roberts, D. A. 1979. Food habits as an ecological partitioning mechanism in the nearshore rockfishes (Sebastes) of Carmel Bay, California. ~1.A. Thesis, San Francisco State University. 77 p. Rosenthal, R. J., W. D. Clarke, and P. K. Dayton. 1974. Ecology and natural history of a stand of giant kelp, Macrocystis pyrifera off Del Mar, Calif. Fish. Bull. 72(3):670-684. Seaburg, K. G. and J. B. Moyle. 1964. Feeding habits, digestive rates and growth of some Minnesota warm water fishes. Trans. Amer. Fish. Soc. 93(3):269-285. 30

Singer, M. M. 1982. Food habit and activity patterns of juvenile rockfishes (Sebastes) in a central California kelp forest. M.A. Thesis, San Jose State University. 75 p. Sakal, R. R. and F. J. Rohlf. 1969. Biometry. W. H. Freeman, New York, 776 p. Swenson, W. A. and L. L. Smith. 1973. Gastric digestion, food consumption, feeding periodicity, and food conversion efficiency in walleye (Stizostedion vitreum vitreum). J. Fish. Res. Bd. Can. 30(9):1327-1336. Tyler, A. V. 1970. Rates of gastric emptying in young cod. J. Fish. Res. Bd. Can. 27(7):1177-1189. Webster, D. A. 1942. Food progression in young white perch, Marone americana (Gmelin) from Bantam Lake, Connecticut. Trans. Amer. Fish. Soc. 72:136-144. Windell, J. T. 1978. Digestion and daily ration of fishes. Pages 159-163 inS. D. Gerking (ed.). Ecology of freshwater fish production. Wiley and Sons, New York. Winer, B. J. 1971. Statistical principles in experimental design. McGraw-Hill Inc., USA. 907 p. Zar, J. H. 1974. Biostatistical Analysis. Prentice-Hall, Inc. Englewood Cliffs, N.J. 620 p. 31

Figure 1. Index map of vicinity of sampling area showing Stillwater Cove at the northern end of Carmel Bay.

- 32

} . :ASILOMAR I : ·.. . : . . . .

MONTEREY PENINSULA

. STILLWATER COVE

PESCADERO POINT ·.·. CARMEL BAY

POINT LOBOS 33

Figure 2. Detail map of Stillwater Cove showing study area. Rock and sand substrata are shown only near the study site. 1r STILLWATER I COVE 0 30 meters

ROCK[Il

ARROWHEAD POINT

CARMEL 20

_, 35

Figure 3. Map illustrating study site and the various zones sampled in the kelp forest. 36

w-' z z E <( I 0 u 0 """ z <( ())

a.. ~ ..J (.) w 0 ~ 0:: 37

Figure 4. Flow diagram illustrating the three-factor ANOVA model. SEASON

DAY._____ T_im_e-_..o_f_d_a_y ____ NIGHT

Vertical Distribution

CANOPY MIDWATER BOTTOM CANOPY MIDWATER BOTTOM

Behavior

w 00 39

Figure 5. Cumulative abundance expressed as mean number of fish versus number of transects. Data are expressed as mean number of fish with the standard error. Data include day and night transects during the kelp season. 40

--+­ ....., I ...t:: I ~ .~ ---t­ lnc.o !:::.) . ~ I -rI I ln + ln I -+- 1 (J) ~ I 0 Q) c (J) 0 c CJJ 0 0v L (f) I ~ I ln4- 0. m o -v :::.::: I L I ISl Q) I m_o .E :J I tn::Z: I N I

\ \

I / I \ \

. . . . • . . m N N .-t .-t ISl ISl 41

Figure 6a. Canopy cover estimates in percent surface cover at Arrowhead Point, Stillwater Cove from ~1ay 1981 to December 1982. 6b. Mean Macrocystis densities and percentage of stipes per plant at Arrowhead Point from March 1982 to January 1983. 42

Kelp Season : Non-Kelp Season Kelp Season 75-100 I I... I I ~ I 0 I 0 I <1l I () 50-75 I 0 I 't: I :::s I Ul I ~ I 25-50

0-25 M J J A S 0 N D J F M A M J J A S 0 N D

MONTHS ( 1981-82)

*= Mean of plants/m2 ±SE 90 # 1. 80 += % plants > 5 stipes :5:: 80 x= % plants ·< 5 stipes 1. 60 (!) a :::s 70 1. 40 z c 1. 20 3 CT .,(!) ~ 50 1- 1. 00 (Jl u .....0 in 40 0. 80 u CL. a 30 0. 60 ::J...... Ul ...... 20 0. 40 3 " 10 0.20

0 L_:t::=:f_____,__ _,__'-----'---'------'----'---__.J''----'--_j 0. 00 M A M J J A s 0 N D J

MONTHS (1982-83) 43

Figure 7. Frequency histograms of number of kelp rockfish per daytime transect for 55 transects each in the kelp (June to October) and non-kelp (November to May) seasons in 1981 to 1982 at Stillwater Cove, Carmel Bay. Abundances were significantly different (Mann-Whitney U test, with Z statistic, p < .05). 44

25 ' ., Kelp Season I I 20 1 .-- ! Number of transects = 55

>-. 15 Number of fish 103 I 0 . = l: (!) ::> r:r (I) 1 I J:: Hl .-- ..-- r-- I - 5

_0 -•- --'- n 1 2 3 5 6 7 8

25 ' ' '

,..-- Non-Kelp Season 20 ~

..-- Number of transects = 55

>-. 15 Number of fish 66 0 = - l: (I) ::> r:r (I) J:: Hl .-- r- 5

n ' 1 2 3 4 5 6 7 8

Number of Fish per 40 m2 Transect 45

Figure 8. Seasonal day and night activity of kelp rockfish based on transect data. Numbers represent actual counts for 55 transects in each zone. 46

25

,.....--- Kelp Season 20 N=54

...r:. DDAY .....(/) . '+- 15 f- '+- [ill] NIGHT 0

(/) L (!) ..0 10 E :z::J - 5 -

25 '

Non-Kelp Season 20 f- N=42

...r:...... (J) '+- 15 f- '+- r-- 0

(J) - L (!) ..0 10 E :J :z:

5

mn I 111111 KELP ROCK SHELTER

Microhabitat 47

Figure 9. Seasonal day and night microhabitat use by kelp rockfish based on 50 transects for each day and night period, with numbers representing actual counts. 4B

35 Kelp Season - Day Kelp Season - Night Canopy 3B N=64 0 N=36 .L tD c.,..-~ 25 [ill Mldwater c.,.. 0 29 00 L ~Bottom il'" 15 :z: " 19

5

B

43

35 Non-Kelp Season - Day Non-Kelp Season - Night

39 N=37 N=24 .L Q) c.,..-~ 25 4- 0 2B (JJ L ..D 15 '"E :z:" 13

5

B ·!(Ill ?-rJ,~ elu~ !(11'~ ?-,.~~ ~fill ,...--/ ~fill~ st"/ s/~ ""'00 ~fill s.JSI'" ~cJll Activity 49

Figure 10. Cumulative number of prey types versus number of stomachs examined for each time of collection. Hl Down N=42 Noon N=17 8 ;1---+-~-+--~ /

Ill Cl) 0.. ~ ~ 2 0...... 0 0 .... Cl) .0 E ::l z 10 Night N=13 Q) Dusk N=46 --+-----+ ~ 0 8 "5 E ::l 0 6 r

4

2

0 10 15 20 25 30 35 40 45 0 5 10 15 20 25 30 35 40 45 fil 5 U1 0 Number of Stomachs Number of Stomachs 51

Figure 11. Percent number and frequency of occurrence of eleven prey types at dawn, noon, dusk, and night for kelp rockfish. 52

100

80 DAWN ,_.~ N=42 ~ 0% Number ..., 60 c (!) lliD % Frequency u t. 40 (!) 0.... 20

0 100

83 NOON ~,_. ~ N=17 ..., 63 c Q) u t. 41:1 (!) 0.... 21:1

3 130

81:1 DUSK ~,_. ~ N=46 ..., 63 c (!) u t. 41:1 (!) 0.... 21:1

l:l Hll:l

81:1 NIGHT I ,_.~ ~ ..., 611 N=13 c (!) u ,- t. 411 (!) 0.... 21l Lc'-- L..r:: _r: LJlnL

Prey Items 53

Figure 12. Fullness-recency data for stomachs collected at dawn, noon, dusk, and at night. There were significantly more full and recent stomachs at dawn and night (X~= 100,63, n = 118; df = 1; p < .05). DAWN N=42 NOON N=17 DUSK N=46 NIGHT N=13 80

>-­ () c 60 Q) :J o­ Q) L LL 40

20 I i n n A B C D A B C D A B C D A B C D Fullness

A;::. Not full or recent s.....: Recent but not full C;::. Full and recent Q;::. Full but not recent 55

Figure 13. Estimated initial feeding time of 19 kelp rockfish from field collections. Only those containing juvenile fishes were examined. 56

I I I I I I I I I [\ .

en c -o Cl) Cl) \ LL.

'+- 0

Cl) E i-- I\

[\

I I I I I I I I I 57

Table 1. Three factor ANOVA comparing season, time of day, and behavior. Cochran's test determined the variances were homogeneous.

Source of Variation df ss MS F A. Season 1 2.189 2.189 22.111 *** B. Time of Day 1 0.836 0.836 8.444 *** c. Behavior 9 55.976 6.220 62.829 *** Resting vs. others 1 3.447 3.447 3.447 D. Vertical Distribution 2 36.632 18.316 185.010 *** E. Behavior 2 12.829 6.414 64.787 *** DxE 4 3.068 0.767 7.747*** AxB 1 0.353 0.353 3.565 Axe 9 11.179 1.242 12.476 *** BxC 9 6.987 0.776 7.798 *** AxBxC 9 2.173 0.241 2.425 *** Residuals 40 3.982 0.099 Total 79

*** = p < 0.05 58

Table 2. Three factor ANOVA comparing season, time of day, and microhabitats. Cochran's test determined that the variances were homogeneous (@ = 0.05).

Source of variation df ss MS F 1. Season 1 0.418 0.418 20.824 *** 2. Time of Day 1 0.998 0.998 49.695 *** 3. Microhabitats 2 5.173 2.586 128.788 *** 1x2 1 0.295 0.295 14.703 *** 1x3 2 4.180 2.090 104.085 *** 2x3 2 2.359 1.179 58.725 *** 1x2x3 2 1.147 0.573 28.548 *** Error 12 0.241 0.020 Residuals 23

*** = p < 0.05 Table 3. Home range observations for 14 tagged kelp rockfish expressed as the number of observations in three categories of distance from the home range. Five fish were tagged on 22 September 1981 and 19 November 1981. Month and Number of Dives per Month

1981 1982 No. of s 0 N D J F M A M J J A s 0 N D % Obs. 1 0 2 1 1 1 2 4 2 4 4 5 1 2 1 3 Tag Distance 0-3 1 1 3 3 3 1 1 2 93.7 1 3.5-6.5 s 0.0 16 7.0-10.5 E 1 6.3 'V

0-3 E 1 2 2 1 2 3 3 1 2 1 1 90.4 2 3.5-6.5 R 1 9.6 21 7.0-10.5 E 0.0 0-3 s 1 2 2 1 1 90.0 3 3.5-6.5 T 1 1 1 30.0 10 7.0-10.5 0 0.0 R 0-3 M 1 2 1 67.0 4 3.5-6.5 s 2 33.0 6 7.0-10.5 0-3 3 75.0 5 3.5-6.5 0.0 4 7.0-10.5 1 25.0

Ul lD Table 3. (continued) Month and Number of Dives per Month 1981 1982 No. of s D N D J F M A M J J A s 0 N D % Obs. 1 D 2 1 1 1 2 4 2 4 4 5 1 2 1 3 Tag Distance 0-3 1 1 67.0 6 3.5-6.5 0.0 3 7.0-10.5 1 33.0 0-3 1 2 75.0 7 3.5-6.5 1 25.0 4 7.0-10.5 0.0 0-3 1 8 3.5-6.5 1 2 7.0-10.5 0-3 1 9 3.5-6.5 1 2 7.5-10.5 0-3 1 10 3.5-6.5 1 7.5-10.5 0-3 1 11 3.5-6.5 1 12 0-3 1 1 13 0 0 14 0 0 C)"' Table 4. Qualitative description of state of digestion indices for juvenile Sebastes eaten by kelp rockfish.

Digestion Interval Sample Percent Index (hrs) Size Eyes Gi 11 s Flesh Rays Vertebrae Digestion 1 3-8 2 Lens not Undigested Pigment Membrane Intact 25-29% separated still digesting or present almost gone 2 g-12 2 Lens Undigested Pigment Membrane Intact 35-39% separated digested or gone, rays very little separated flesh intact 3 13-24 3 Lens Partially Cylindrical Gone Intact, 48-57% separated gone, head mass sur- covered digesting. rounding by flesh vertebrae 4 25+ 2 Gone Gills Elongate Gone Connected 65-98% digested, cylindrical but exposed, head lumps surrounded digested by flesh