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Site Fidelity And Depth Preference Of Nearshore Reef Fishes On San Pedro Shelf Offshore Petroleum Platforms Website

Principal Investigator(s):
Christopher G. Lowe - Dept. of Biological Sciences, California State University, Long Beach
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Associate Investigator(s):
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Period: 1/1/2007 - 2/1/2009

Current Status: Completed Last Updated: 8/18/2010
Federal Funds: State Funds:

Objectives:
The objectives of this study are to 1) assess the site fidelity of nearshore reef fishes to petroleum platforms on the San Pedro Shelf, 2) assess the depth preference of the same species relative to environmental conditions, and 3) compare the site fidelity of nearshore reef fish on petroleum platforms on the San Pedro Basin with site fidelity of rockfish species on petroleum platforms in the Santa Barbara Channel.

Methodology:
Forty nearshore reef fish of economically important species, particularly California sheephead, cabezon, kelp bass, and kelp rockfish, will be caught at two petroleum platforms on the San Pedro Shelf and surgically implanted with a coded acoustic transmitter. An additional 20 fish will be fitted with depth-sensing coded acoustic transmitters. Tagged fish will be measured, weighed, tagged and then released at the point of capture. The fish will be continuously monitored over an 18 month period using automated acoustic receivers, oriented to maximize signal acquisition. Site fidelity will be assessed using presence/absence data over days at liberty and depth data will be used to assay for any cyclical movements and depth preference relative to environmental conditions.

Rationale:
Many of the 27 petroleum platforms found off of California are forecast to end production in the next decade, which has heightened the debate regarding their decommissioning. Currently, California requires complete removal of decommissioned platforms, although there is growing evidence that these structures have larger individuals and higher abundances of economically important fish than adjacent natural reefs. These increased numbers of fish associated with offshore platforms compared to natural reefs have been attributed to the differences in fishing pressure and extraction efficiency, thereby allowing these platforms to function as de facto marine reserves. A majority of the research done on fish population around offshore platforms have focused on those in the Santa Barbara Channel; however, relatively little is known about the fishes associated with the southern most platforms on the San Pedro Shelf, where rocky habitat is less abundant and urban influences from the heavily populated Los Angeles and Orange Counties have degraded much of the coastal habitat. Preliminary observations indicate that nearshore reef fish may dominate San Pedro Shelf platforms, while rockfishes tend to dominate the more northern platforms. In addition, it is essential to know whether the fish that are observed on these platforms are residents of these platforms. If fish on offshore platforms in the San Pedro Basin show high site fidelity, these structures could be as ecologically important as those in the Santa Barbara Channel. Therefore, any complete removal of these could have significant impacts on adjacent marine communities and local fisheries. Knowledge gained from this study will be used to assess the ecological importance of petroleum platforms on the San Pedro Shelf which will help shape any potential “rigs-to-reefs” policy in California. Additionally, information on site fidelity and depth preference will be of value to resource managers in designing future artificial reef habitat and marine reserves.

Accomplishments:
Site fidelity of cabezon, grass rockfish, kelp rockfish, and California sheephead

At the end of the study (1 January 2009), 12 of the 63 fish tagged were detected 100% of the days that they were at liberty (Table 1), which included 3 grass rockfish (ID# 187, 2973, 2991) (Figure 2b), 3 kelp rockfish (ID# 185, 2971, 2974) ( Figure 2c), and 6 sheephead (ID# 2, 186, 193, 2972, 2977, 2978) (Figure 2d), with no cabezon individuals detected 100% of the days (Figure 2a). Over the entire duration of the study (17 June 2007 to 1 January 2009), all tagged individuals were detected a mean (± SD) of 66.9 ± 36.0 % (Table 1) of their total days at liberty, which ranged from 445-578 d, depending on when the individual was tagged (Table 2). A detailed description of the daily site fidelity by species and platform over the entire study are presented in Table 1. In comparisons of annual daily site fidelity from 1 September 2007 to 31 August 2008, sheephead displayed a significantly higher probability of being present on any given day than cabezon (Mann-Whitney, U = 309.0, df = 29, p = 0.0016). At the end of the study (1 January 2009) 80% of sheephead individuals were still detected at platforms, followed by grass rockfish (61.5%), kelp rockfish (58.3%), and cabezon (50.0%) (Table 2). A higher percentage of cabezon, grass rockfish, and kelp rockfish individuals displayed overall site fidelity at platform Eureka (71.4%, 66.7%, and 66.7%, respectively) than platform Edith (28.6 %, 57.2 %, and 50.0 %, respectively), with a higher percentage of sheephead still present at platform Edith (87.5%) than at Eureka (71.4%)(Table 2). Only one fish was detected at another platform other than its site of capture and release. One cabezon moved from platform Eureka on 7 July 2007 and was then detected at platform Elly on 17 July 2007, where it remained until at least 15 January 2009 (Figure 2).
Comparisons of daily site fidelity by season for cabezon indicated they were detected a significantly lower proportion of days during Summer 2008 than in Fall 2007 (Mann-Whitney, U = 46.50, df = 13, p = 0.016) and Winter 2008 (U = 48.00, df = 13, p = 0.019), which was a result of the emigration of 3 individuals (ID# 1,199, and 3001) from platform Edith and lapses in daily detections of 3 individuals (ID# 197, 2984, and 2986) on platform Eureka during Summer 2008 (Figure 3a). Grass rockfish were detected a significantly lower proportion of days during Winter 2008 than Fall 2007 (U = 43.00, df = 12, p = 0.019), which was likely due to the emigration of 2 grass rockfish individuals from platform Edith (ID# 182 and 3006) and 2 individuals from Eureka (ID# 181 and 2992) during the Winter 2008 (Figure 3b ). No seasonal differences in daily site fidelity were found for kelp rockfish or sheephead.

TABLE 1. Summary of the Minimum, Maximum, and Mean (± Standard Deviation
(SD)) Percentage of Days That Each Species Was Detected at Platform Edith, Eureka, and Both Platforms Combined (Total) During Their Times at Liberty From 17 June 2008 to 15 January 2009
Species
Platform
Total number of fish analyzed
Minimum percentage of days detected
Maximum percentage of days detected
Mean (± SD) percentage of days detected

cabezon
Edith
8
2.0
94
69.0 ± 29.0


Eureka
7
23.6
98
53.3 ± 38.5


Total
15
2.0
98
61.7 ± 33.5








grass rockfish rockfish
Edith
7
33.0
100
70.1 ± 31.5


Eureka
6
23.6
100
52.6 ± 37.0


Total
13
23.6
100
62.0 ± 33.8








kelp rockfish
Edith
5
24.3
100
80.4 ± 32.7


Eureka
5
7.0
100
45.8 ± 47.3


Total
12
7.0
100
63.1 ± 42.4








sheephead
Edith
8
16.1
100
86.0 ± 28.8


Eureka
7
50.0
100
89.7 ± 19.1


Total
15
16.1
100
87.8 ± 24.0








All Species
Edith
29
0.5
100
73.6 ± 32.1


Eureka
26
23.6
100
59.5 ± 39.1


Total
55
0.5
100
66.9 ± 36.0
























FIGURE 2. Daily detection plots of tagged a) cabezon, b) grass rockfish, c) kelp rockfish, and d) sheephead. Each vertical dash indicates the presence of individuals on a given date on platform Edith (gray dashes) and Eureka (black dashes). Box around detections of cabezon ID# 2979 indicate detections that occurred on platform Elly after this individual moved from platform Eureka.
TABLE 2. Summary of the Number and Percentage of Individuals Still Present at Platforms at the End of the Study on 1 January 2009.

Species
Platform
Total number of fish analyzed
Number of individuals present at the end of study
Percentage of total number of individuals present at the end of study
Range of the minimum and maximum number of days at liberty for individuals present at end of the study

cabezon
Edith
7
2
28.6
545-564


Eureka
7
5
71.4
543-570


Total
14
7
50.0
543-570








grass rockfish
Edith
7
4
57.2
524-565


Eureka
6
4
66.7
548-572


Total
13
8
61.5
524-572








kelp rockfish
Edith
6
3
50.0
571-573


Eureka
6
4
66.7
569-572


Total
12
7
58.3
569-573








sheephead
Edith
8
7
87.5
546-573


Eureka
7
5
71.4
445-578


Total
15
12
80.0









All Species
Edith
29
16
55.2
524-573


Eureka
26
18
69.2
445-578


Total
55
34
61.8
445-578











FIGURE 3. Seasonal comparisons of daily site fidelity within species amongst Fall 2007, Winter 2008, Spring 2008, and Summer 2008. Open circles represent the percentage of days that individuals were detected within each season with solid black squares representing the species median daily site fidelity. Large bars indicate means with error bars indicating 95 % confidence intervals of the mean.


Vertical movement and depth utilization of cabezon, grass rockfish, kelp rockfish, and California sheephead

Over the study period (June 2007-January 2009), cabezon were detected throughout most of the depths of platforms Edith (ID# 1, 198, and 199) and Eureka (ID# 188 and 197) (Figure 4). Four cabezon individuals progressively utilized deeper areas of each platform in the Summers of 2007 (ID# 188) and 2008 (ID# 1, 199, and 197), with detections ceasing completely by early September 2008 for both ID# 1 and 199 on platform Edith. Grass rockfish tagged with depth sensing transmitters displayed primarily shallow depth utilization (~16 m) on both platforms Eureka (ID# 181 and 187) and Edith (ID# 182 and 189) throughout the study, with ID# 182 and 189 occasionally making short duration movements to deeper depths (~30 m) (Figure 5). Both ID# 181 and 182 displayed movement to deeper depths prior to detections ceasing completely for these individuals in late November 2007 and early December 2008, respectively. Kelp rockfish on platform Eureka (ID# 191, 192, 194, and 196) were detected from shallow depths (~10 m) down to depths deeper than the bottom of the platform (> 220 m), while individuals on platform Edith (ID# 180 and 185) exhibited primarily shallow depth utilization (15-30 m) over the duration of the study (Figure 6). Kelp rockfish ID# 180 on platform Edith displayed its deepest depth detection (45 m) prior to a sudden loss of detections on 14 September 2008.
Sheephead on both platform Edith (ID# 193 and 195) and Eureka (ID# 2, 184, and 186) utilized depths between 10 and 55 m, with fish ID# 2, 184, 186, and 193 primarily being detected at shallow depths (10-20 m) (Figure 7). Sheephead ID# 195 (female) displayed opposite behavior by primarily being detected deep (50 m) while making occasional movements to shallow depths between June 2007 and December 2007, after which time this individual primarily utilized shallow areas until detections discontinued in mid September 2008. Patterns in utilization of deeper depths were evident during Winter 2008, Summer 2008, and Winter 2009 for sheephead ID# 2, 184, 186, and 193. Distinct patterns in movement to deeper depths were often exhibited by multiple sheephead individuals (ID# 2, 184, 186, and 195), with examples of these events occurring between 15-18 June 2008 and again between 20-30 September 2008.
Differences in seasonal depth utilization were found for cabezon (Kruskall Wallis, H = 159.45, df = 3, p < 0.001) (Figure 8a), grass rockfish (H = 83.20, df = 3, p < 0.001) (Figure 8b), kelp rockfish (H = 99.47, df = 3, p < 0.001) (Figure 8c), and sheephead (H = 135.16, df = 3, p < 0.001) (Figure 8d). Results of seasonal pairwise comparisons are presented in Table 3.















FIGURE 4. Time series depth plots (black line) of cabezon individuals on platform Edith and Eureka overlying water temperature (oC) profiles (color gradient) measured from 5-30 m depths. Temperature (oC) is coded by color with red indicating warmer water and purple indicating colder water (see legend). Horizontal black lines at 50 and 212 m represent the bottom depth of platform Edith and Eureka, respectively.

FIGURE 5. Time series depth plots (black line) of grass rockfish individuals on platform Edith and Eureka overlying water temperature (oC) profiles (color gradient) measured from 5-30 m depths. Temperature (oC) is coded by color with red indicating warmer water and purple indicating colder water (see legend). Horizontal black line at 50 m represents the bottom depth of platform Edith.

FIGURE 6. Time series depth plots (black line) of kelp rockfish individuals on platform Edith and Eureka overlying water temperature (oC) profiles (color gradient) measured from 5-30 m depths. Temperature (oC) is coded by color with red indicating warmer water and purple indicating colder water (see legend). Horizontal black lines at 50 and 212 m represent the bottom depth of platform Edith and Eureka, respectively.

FIGURE 7. Time series depth plots (black line) of California sheephead individuals on platform Edith and Eureka overlying water temperature (oC) profiles (color gradient) measured from 5-30 m depths. Temperature (oC) is coded by color with red indicating warmer water and purple indicating colder water (see legend). Horizontal black lines at 50 and 212 m represent the bottom depth of platform Edith and Eureka, respectively.


FIGURE 8. Comparisons of mean daily depths pooled by season for a) cabezon, b) grass rockfish, c) kelp rockfish, and d) sheephead. Significant seasonal differences (p < 0.05) are represented by letters above or below boxes which indicate the season from which that seasonal category differs (A = Fall 2007, B = Winter 2008, C = Spring 2008, D = Summer 2008). Boxes represent the interquartile range (middle 50%) of data points, with the lower and upper line of the box extending to the 25th and 75th percentile of the data, respectively. The line within the box indicates the median, open circles represent the mean, and solid black circles represent outliers. The lower and upper whiskers extend to the minimum and maximum data points within 1.5 box heights from the box. Note y-scale range differs for each species.


The daily mean temperature difference between 5 and 30 m (Figure 9) was found to have a significant effect on the daytime depth distribution of sheephead (p < 0.001, df = 6, H = 33.419) (Figure 10) and the daily depth distribution of cabezon on platform Edith (p < 0.050, df = 7, H = 129.76) (Figure 11). Sheephead were detected significantly shallower during daytime hours (09:00-16:00 h) and cabezon were detected significantly deeper on a daily basis as the temperature difference between 5 and 30 m increased.



FIGURE 9. Mean daily water temperature (oC) difference between 5 and 30 m depths by date.



FIGURE 10. California sheephead mean daytime (09:00-15:59 h) depths (m) by daily temperature (oC) differences between 5 and 30 m depths for all depth sensing transmitter tagged individuals on both platforms. The numbers above each box indicate the temperature difference categories from which they are significantly different (p < 0.05). Boxes represent the interquartile range (middle 50%) of data points, with the lower and upper line of the box extending to the 25th and 75th percentile of the data, respectively. The line within the box indicates the median, open circles represent the mean, and solid black circles represent outliers. The lower and upper whiskers extend to the minimum and maximum data points within 1.5 box heights from the box.



FIGURE 11. Cabezon mean daily depth (m) vs. the mean daily temperature difference (oC) between 5 and 30 m depths for all depth sensing transmitter tagged individuals on platform Edith. The numbers above each box indicate the temperature difference categories from which they are significantly different (p < 0.05). Boxes represent the interquartile range (middle 50%) of data points, with the lower and upper line of the box extending to the 25th and 75th percentile of the data, respectively. The line within the box indicates the median, open circles represent the mean, and solid black circles represent outliers. The lower and upper whiskers extend to the minimum and maximum data points within 1.5 box heights from the box.


Out of all depth detections for cabezon on platform Edith, 69.0% occurred in close proximity (< 3 m) of all horizontal levels (Figure 12a), with a majority of all depth detections (63.5%) occurring within 3 m of the 2nd horizontal level (30 m depth) (Figure 14). On platform Eureka, cabezon did not utilize horizontal depth levels as frequently as on platform Edith, with only 17.6% of detections occurring within 3 m of horizontal depth levels (Figure 14). Overall, on both platforms, a majority of cabezon detections (58.7%) were associated with non-horizontal level areas.
A majority of grass rockfish detections occurred within close proximity of all horizontal levels on both platforms Edith (90.3%) and Eureka (99.4 %) (Figure 12b). Overall, 96.2% of all grass rockfish depth detections on both platforms (460,181 of 478,275 total detections) occurred within 3 m of a horizontal level (Figure 14). Grass rockfish displayed the highest percentage of total depth detections within 3 m of the shallowest horizontal level on both platforms Edith (89.9%) and Eureka (99.4%)(Figure 14).
Kelp rockfish depth detections occurred most frequently within 3 m of a horizontal level on platform Edith (91.8% of total detections) and Eureka (61.4%) (Figure 13a). On both platforms, 91.7% of kelp rockfish detections occurred at depths less than 3 m from a horizontal level. On platform Edith 91.3% of detections occurred within 3 m of the shallowest horizontal level, while on platform Eureka 41.5% of detections occurred within 3 m of the shallowest level (Figure 14). Kelp rockfish on platform Eureka also displayed 12.7% of their total depth detections within 3 m of the 60 m horizontal level (Figure 14).
A majority of sheephead depth detections (54.3%) on platform Edith occurred at depths greater than 3 m from a horizontal level, with most depth detections on platform Eureka (61.7%) occurring in close proximity (< 3m) to a horizontal level (Figure 13b). On both platforms combined, 58.1% of all sheephead depth detections occurred close to horizontal levels (< 3 m). On platform Edith, 42.1% of the total depth detections occurred within 3 m of the 1st horizontal level with 38% of the total depth detections occurring shallower than the first level (0-11 m depths) (Figure 14). On platform Eureka, 57% of all 196,714 depth detections occurred within 3 m of the first horizontal level, with 27.6% of the total detections occurring shallower than the level (0-13 m depths) (Figure 14).
Across all study species, 86.0% of 753,875 total depth detections occurred within 3 m of a horizontal level on platform Edith with 76.1% of 580,612 total depth detections occurring within 3 m of a horizontal level on platform Eureka. Out of all depth detections across both platforms (1,334,487 total), 81.7 % occurred within 3 m of a horizontal level.
FIGURE 12. Log frequency of detections at depth for a) cabezon and b) grass rockfish on platform Eureka (212 m depth, left) and Edith (50 m depth, right). Dashed lines represent platform horizontal levels with the solid line representing platform bottom.

FIGURE 13. Log frequency of detections at depth for a) kelp rockfish and b) sheephead on platform Eureka (212 m depth, left) and Edith (50 m depth, right). Dashed lines represent platform horizontal levels with the solid line representing platform bottom. 
FIGURE 14. Percentage of depth detections associated with specific horizontal levels (shaded gray bars) and depths in between horizontal levels (non-shaded areas) indicated by y-axis labels without denotation on platform Eureka (a) and Edith (b).
Comparisons of site fidelity with species inhabiting platforms on the Santa Barbara Channel (SBC)

Over the entire study period (1.5 yrs.), the daily site fidelity of all individuals did not differ between platform Edith and Eureka suggesting that both platforms function similarly in supporting individuals on a daily basis for extended periods of time. Findings of daily site fidelity demonstrate that all individuals were present at platforms a mean (± SD) of 66.9 ± 36.0% of the total days that they were at liberty. Considering the site fidelity scale proposed by Lowe et al. (2009), degrees of daily site fidelity would be considered to be high for all four species. In Lowe et al (2009), 3 species (lingcod (Ophiodon elongates), treefish (Sebastes serriceps), and flag rockfish (Sebastes rubrivinctus)) displayed similar high daily site fidelity to platforms in the SBC, cabezon along with 4 species of rockfish were found to display moderate daily site fidelity, and 7 rockfish species displayed low daily site fidelity. Low degrees of daily site fidelity displayed by species on SBC platforms, was related to the high rates of movement away from platforms, which included movement between platforms that were approximately 5 km apart for eight vermilion rockfish and one copper rockfish, as well as movement to natural reef by one lingcod (Lowe et al., 2009). On offshore SPS platforms located as close as 2 km from each other, only one individual (cabezon) displayed inter-platform movement and all species on the SPS displayed higher rates of daily site fidelity than a majority of species on the SBC. Considering these difference in site fidelity between SBC and SPS platforms, nearshore species inhabiting offshore SPS platforms may be more dependent on platform habitats to support them on a daily basis. In the eastern SBC where there is greater amounts of shallow natural reef, adult sheephead and kelp rockfish both displayed higher densities at natural reef than adjacent platforms (Carr et al., 2003), suggesting that platforms may not be as beneficial to these nearshore species when natural reef is available. However, on the SPS shallow hard rocky reefs (both natural and artificial) occurring in depths similar to those most used by grass rockfish, kelp rockfish, and sheephead on platforms (< 20 m) are extremely limited, and in most cases possibly too far away (> 12 km). Since platform Eureka is much deeper (212 m) than the depths that these nearshore species have been previously known to utilize (Eschmeyer, 1983; Love, 1996), an emigration event would likely involve swimming in open water for long periods of time, which may be too high of a risk for these species which primarily associate with hard substrate. The fact that a majority of individuals remained at platforms when others emigrated, suggests that density dependent factors may also play a large role in site fidelity to platforms. SUMMARY
Findings in this study suggest that SPS platforms provide important habitat for adults of nearshore reef fishes, which is supported by findings that individuals are sheltering and foraging at platforms for extended periods of time. All four study species displayed high rates of site fidelity to SPS platforms for periods up to at least 1.5 yrs. The rates of site fidelity were found to be higher than those displayed by a majority of species inhabiting platforms on the SBC. Each species displayed seasonal differences in depth utilization, suggesting that individuals make vertical movements within platform habitats to meet biological demands. Vertical movements may be associated with factors relating to thermocline, with both cabezon and sheephead displaying changes in depth utilization related to temperature. Regardless of overall platform depth, the most important aspect of habitat on both platforms was demonstrated to be the horizontal levels, with all species with the exception of cabezon, mainly utilizing depths within close proximity (< 3 m) to horizontal levels. Findings are supported by other artificial reefs studies that found reef fish to mostly utilize horizontal substrate when presented with various aspects of habitat (Grove, Sonu, and Nakamura, 1989). During sheltering and foraging activities, species appear to utilize the tops of these levels as hard seafloor while utilizing the undersides of the levels as reef overhangs or kelp canopy. The first horizontal level on platform Edith (15 m) and platform Eureka (17 m) was found to be the most utilized aspect of habitat by grass rockfish, kelp rockfish, and sheephead, as well being used by all study species during their known spawning periods.
If a reefing program is adopted in California, then the various proposed decommissioning options with the exception of no removal, could eliminate the habitats most used by the four study species. In particular, decommissioning options which include the removal of the shallow horizontal level located on platform Edith at 15 m and on platform Eureka at 17 m would eliminate the only aspect of habitat utilized by all four study species. The decommissioning option of partial removal, which removes shallower portions of platform habitat to a designated depth, could retain the habitats most used by nearshore fishes if portions of the structure are not removed deeper than the first horizontal level. Toppling, which lays the structure horizontally along the bottom, could also provide habitat to the four study species if the top of the reefed structure extends to within at least 15 m of the surface. If platforms are toppled in their current location, then platform Edith is wide enough to still extend to the surface, providing the shallow habitat required by these nearshore species. However, if Eureka were toppled in its current location, the structure would reside deeper than depths most utilized by nearshore species in this study. In addition, if platforms were toppled the horizontal levels would be re-oriented vertically, which may change the ecological importance of these structures to nearshore species. If platform structures are relocated to new areas after being completely removed, they would need to be placed in a similar manner as discussed above for partial removal and toppling to provide habitat to the nearshore species in this study. In addition, toppling and complete removal requires the use of explosives to remove structures from the seabed, which results in the death of most resident fishes and invertebrates (Schroeder and Love, 2004). The decommissioning option of no removal would likely have the least affect on nearshore species currently residing at offshore SPS platforms; however, to date no platform has been fully retained, which is likely due to the estimated costs of maintaining the structure ($300,000 per yr) (Love et al., 2003). Any structure that is retained as fisheries habitat may also be enhanced through the addition of hard materials such as quarry rocks (Schroeder and Love, 2004). If enhancements were made to platforms, the four nearshore species in this study would likely benefit most from horizontal types of structural additions placed in depths ranging from 15 to 30 m.
These findings are the first to describe the fine-scale site fidelity, vertical movements, and habitat utilization of economically important species inhabiting California petroleum platforms. These results demonstrate the potential ecological consequences of the various proposed decommissioning options on adults of cabezon, grass rockfish, kelp rockfish, and California sheephead inhabiting SPS platforms. Data from this study has been shared with members of the consulting group led by Brock Bernstein to evaluate ecological importance of petroleum platforms as fisheries habitat and will be important in determining the most appropriate decommissioning option to meet conservation goals in California.

Outcomes:

Publications & other print media:
Fine-scale movement patterns, site fidelity, and habitat selection of ocean whitefish (Caulolatilus princeps)
Lyall F. Bellquist, Christopher G. Lowe, Jennifer E. Caselle, 2007

The fishery for California groundfishes is managed using broad species complexes, although some non-groundfish species are managed similarly due to the perception of shared behavioral characteristics. This study integrates acoustic telemetry and a GIS to quantify movement patterns of one such species, the ocean whitefish (Caulolatilus princeps) in a marine protected area. Seventeen ocean whitefish were tagged and actively tracked over multiple 24-h periods to measure fine-scale movement patterns. Home ranges based on 95% kernel utilization distributions averaged 20,439±28,492 (±S.D.)m2. Fish were active during the day, foraging over sand habitat at depths averaging 21±8m, but were inactive at night, taking refuge near rocky reefs at depths averaging 15±7m. Seventeen additional fish were tagged with coded acoustic transmitters and passively tracked using automated underwater acoustic receivers for up to 1 year. Approximately 75% of these fish exhibited long-term (1 year) fidelity to home ranges in the study area. Results suggest that MPAs can be an effective means of protecting populations of ocean whitefish and based on their habitat associations, ocean whitefish can be managed separately from other reef associated groundfishes.
© 2007 Elsevier B.V. All rights reserved.

PDF http://www.usc.edu/org/seagrant/Publications/PDFs/Bellquist-et-al_movementofOWF.pdf

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