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Life-history aspects of the Yellow Irish Lord (Hemilepidotus jordani) in the Eastern Bering Sea and Aleutian Islands.

ABSTRACT--Growth, reproduction, and diet of the Yellow Irish Lord (Hemilepidotus jordani) were examined and compared between 2 adjacent geographical regions of Alaska, the eastern Bering Sea and Aleutian Islands, where its biology is not well understood. The Yellow Irish Lord is the most common member of the genus Hemilepidotus encountered during Alaska Fisheries Science Center bottom-trawl surveys of these regions. Based on our data, there was no significant difference in sizes of Yellow Irish Lords caught between regions. The von Bertalanffy growth models fitted to length-at-age data, however, indicate that male and female Yellow Irish Lords in the Aleutian Islands grew more slowly than those in the eastern Bering Sea. Histological assessment of ovary condition indicated that Yellow Irish Lords from both regions appear to spawn once annually during the summer. Relationships between size (length and weight) and fecundity between the 2 regions were significantly different, with Yellow Irish Lords from the Aleutian Islands being more fecund. Diet analysis showed that the Yellow Irish Lord is a benthic predator and their summer diets in both regions consist of a wide variety of prey, but appear to favor benthic crustaceans, particularly abundant crab species. However, the largest individuals appear to have more opportunities for piscivory in the Aleutian Islands. It appears that at least some variation in the life-history aspects of this species exists between these regions. This information may provide a scientific basis for developing management strategies of the Yellow Irish Lord in Alaskan waters.

Key words: Aleutian Islands, diet, eastern Bering Sea, fecundity, growth, Hemilepidotus jordani, life history, Yellow Irish Lord

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The Yellow Irish Lord (Hemilepidotus jordani Bean, 1881), a member of the family Cottidae, inhabits North Pacific Ocean waters (Peden 1978). The Yellow Irish Lord ranges from the northern Kuril Islands and Kamchatka to the eastern Bering Sea and Aleutian Islands, south to the Gulf of Alaska (Allen and Smith 1988). It is a demersal species associated with both soft and rocky substrates at subtidal depths to 110 m, and rarely found deeper than 250 m (Mecklenburg and others 2002). According to data reported from regional trawl surveys conducted by the Alaska Fisheries Science Center (AFSC), the Yellow Irish Lord is the most abundant species of Hemilepidotus in Alaskan waters (Lauth and Acuna 2007; Rooper 2008). This species is commonly caught as bycatch in Alaskan bottom trawl, longline, and pot fisheries (Reuter and TenBrink 2008).

In Alaska, 2 unique neighboring geographical regions are present, the eastern Bering Sea and Aleutian Islands. The eastern Bering Sea continental shelf consists of 3 main oceanographic domains associated with bottom depths (inner, 0-50 m; middle, 50-100 m; and outer, 100-200 m); distinct regions exhibiting unique patterns of oceanic and biological processes (Bakkala 1993; Schumacher and Stabeno 1998; Stabeno and others 2001). The Aleutian Islands archipelago ranges approximately 1800 km from Unimak Island in the Alaska Peninsula to the Commander Islands near the Kamchatka Peninsula. This ecosystem is characterized by a narrow continental shelf, steep continental slopes, and oceanic passes that act as conduits between the Bering Sea and the North Pacific Ocean. Existing information on the Aleutian Islands indicates a change in the species composition and diet of groundfish at Samalga Pass (169[degrees]W) (Logerwell and others 2005), posing the possibility that the life history of the Yellow Irish Lord in the Aleutian Islands may differ from neighboring ecosystems.

The main objective of this paper was to address biological data gaps (growth, reproduction, and diet) of the Yellow Irish Lord from eastern Bering Sea and Aleutian Island waters. We also compare life-history aspects of the Yellow Irish Lord from these 2 regions to describe possible regional variation. Results from this study may provide a scientific basis for developing management strategies for the Yellow Irish Lord in Alaskan waters.

METHODS

Field Collections

Yellow Irish Lords were sampled to collect otoliths for age and growth determinations, ovaries for assessing seasonal reproductive development, and stomachs for diet analysis. Sampling was conducted in 1994, and from 2005 to 2008 along the eastern Bering Sea continental shelf and the Aleutian Islands archipelago (Table 1). Samples from the eastern Bering Sea were collected during AFSC bottom trawl surveys in 1994, 2005, 2006, and 2007; independent scientific cruises in 2007 and 2008; and commercial fishery operations in 2008. Samples from the Aleutian Islands were collected during the 2006 AFSC bottom-trawl survey and aboard commercial fishing vessels in 2005 and 2007. Yellow Irish Lords sampled during bottom-trawl surveys were selected randomly or based on length-stratified sampling schemes for sex and size compositions (fork length [FL] to the nearest 1.0 cm; Lauth and Acuna 2007; Rooper 2008). The eastern Bering Sea shelf has been surveyed by the AFSC using standard methods each summer since 1982. The sampling design is a fixed-station design with I station at the center of a 20 x 20 nautical-mile transect grid and 376 stations covering the survey area (Lauth and Acuna 2007). The Aleutian Islands survey design is based on allocating sampling stations in trawlable habitat in each of the designated strata across the Aleutian archipelago (Rooper 2008). Fishing gear and protocols for deployment are described in Stauffer (2004). Specimens from commercial fishing operations were both randomly and opportunistically sampled. During the trawl surveys, fish were subsampled for otolith collections based on a length-stratified sampling scheme. Otoliths were stored in 70% ethanol, and ovaries and stomachs were fixed in 10% formalin. For the stomach collection, we avoided specimens exhibiting signs of regurgitation or net-feeding and we sampled specimens from as wide a range of lengths as possible.

Size and Growth

Size and growth characteristics of Yellow Irish Lords were investigated to determine if significant differences occur between regions. Length distributions were compared using the Kolmogorov-Smirnov test. Otoliths were processed and ages assigned using the method described in Hutchinson and TenBrink (2011). From these ages, fish growth was described by the von Bertalanffy growth model using lengthat-age data and non-linear least squares regression, [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] where [L.sub.t] = fish length (FL, cm) at age t; [L.sub.[infinity]] = asymptotic maximum fish length (FL, cm); k = instantaneous growth coefficient; t = age (years); and [t.sub.0] = theoretical age (years) at [L.sub.t] = 0. To compare growth curves between regions, an analysis of the residual sum of squares (ARSS) was performed (Chen and others 1992).

Reproduction

To determine the ovarian development stage of females, histological characteristics were recorded using methods described in Hunter and Macewicz (1985) and Hunter and others (1992). The presence of the most advanced stage of oocyte in each ovary was recorded. Potential annual fecundity ([F.sub.P]) was estimated with the gravimetric method (Bagenal and Braum 1978) using ovaries that exhibited advanced stages of vitellogenesis. To minimize bias, differences in oocyte density among 3 locations in each ovarian lobe were tested from 12 fish using a two-way ANOVA to determine if the sampling location affected the fecundity estimate. Fecundity was calculated using the following formula: [F.sub.P] = ([W.sub.O]/ [W.sub.S]) N, where [W.sub.O] is the weight of the ovary after fixation, [W.sub.S] is the weight of the subsample, and N represents the number of oocytes counted in the subsample. Ovary sampling for fecundity estimation followed the methods described by Gundersen and others (2001). The relationship between size (FL and weight) and fecundity was described by best-fitting functions (power or linear) and an analysis of covariance (ANCOVA) was used to test for differences in relationships between regions.

Diet

Stomachs were analyzed in the laboratory to provide detailed food-habit information. Samples that were fixed in 10% formalin were neutralized, rinsed with water, and then preserved in 70% ethanol until analysis. Stomach contents were sorted, identified to the lowest taxonomic level possible, enumerated, and weighed to the nearest 0.001 g. The following measures were used to quantify the importance of prey in the diet among the samples containing food: percent frequency of its occurrence (%FO); its contribution to the total numbers of prey items found, percent number (%N); and its contribution to the total weight of the stomach contents, percent weight (%W). In addition, changes in diet with size were analyzed by dividing sampled specimens into 5 length classes and combining prey taxa into broad prey categories. The carapace width of Chionoecetes spp. (herein referred to as Chionoecetes, which includes both Tanner Crab, C. bairdi, and Snow Crab, C. opilio) in the stomach contents were plotted against the size of Yellow Irish Lords that consumed them.

RESULTS

Size and Growth

Length distributions of Yellow Irish Lords caught in the eastern Bering Sea and Aleutian Islands were similar and showed no significant difference (Kolmogorov-Smirnov, P = 0.057; Fig. 1). The sizes of males and females within each region were also similar (t-test, P > 0.05). Yellow Irish Lords from the eastern Bering Sea ranged from 10 to 50 cm FL (= 34.2 cm; n = 1096), and Yellow Irish Lords from the Aleutian Islands ranged from 12 to 53 cm FL (= 34.9 cm; n = 1099).

A total of 789 otoliths were collected, and 784 were aged (Hutchinson and TenBrink 2011) and used for growth analysis between regions. Growth was significantly different between regions for both males (ARSS, P = 0.02) and females (ARSS, P = 0.001). According to the von Bertalanffy growth model, males and females in the Aleutian Islands had greater asymptotic lengths ([L.sub.[infinity]]) and exhibited slower overall growth (coefficient k) than males and females in the eastern Bering Sea (Table 2; Fig. 2).

Reproduction

In June and July, advanced stages of vitellogenic oocytes were observed without any signs of replenishment from earlier vitellogenic stages, indicative of a type of spawning strategy in which eggs are released in a single event during the spawning period, rather than in batches. Oocytes from a few ovaries collected in late June and early July exhibited signs of hydration, suggesting that spawning had begun at this time. Overall, specimens appeared to be developing during February and March and spawning or near spawning in June and July. The presence of degenerating post-ovulatory follicles with pre-vitellogenic stage oocytes were observed in eastern Bering Sea specimens by September, indicating a spent stage of development. In the Aleutian Islands, advanced vitellogenesis was observed in specimens in June-August, with a few individuals spawning, as evidenced by the presence of hydrated oocytes. By October, Yellow Irish Lords appeared to be spent in this region.

Fecundity estimation was based on random samples throughout each ovary (two-way ANOVA, P = 0.933). Fecundity from 31 fish in the eastern Bering Sea ranged from 54,616 to 224,508 oocytes ([bar.x] = 135,738, s = 43,672; size range: 34-46 cm). A total of 64 specimens collected from the Aleutian Islands exhibited fecundity ranging from 62,020 to 389,378 oocytes/female for 31 to 50 cm fish ([bar.x] = 155,592, s = 68,130). Relative fecundity for specimens from the eastern Bering Sea and Aleutian Islands was 141.1 oocytes/g (s = 23.2) and 163.5 oocytes/g (s = 43.7), respectively. Differences in the size and fecundity relationships between regions existed (ANCOVA, P = 0.002 with FL; P = 0.003 with weight). The relationship between FL and fecundity was best described by the power function with the following equations: eastern Bering Sea: [F.sub.P] = 0.376 x [FL.sup.3.444], [r.sup.2] = 0.70, n = 31; Aleutian Islands: [F.sub.P] = 1.531 x [FL.sup.3.102], [r.sup.2] = 0.67, n = 64. For the comparison between weight and fecundity, a linear function was used: eastern Bering Sea: [F.sub.P] = 156.14(weight) - 13,356, [r.sup.2] = 0.76, n = 31; Aleutian Islands: [F.sub.P] = 154.43(weight) + 6191.3, [r.sup.2] = 0.82, n = 62.

Diet

The stomach contents of 155 Yellow Irish Lords from the eastern Bering Sea and 161 from the Aleutian Islands were analyzed (Table 3). A wide variety of prey was eaten, and empty stomachs were infrequently encountered. In the eastern Bering Sea, the gravimetric composition of the diet was dominated by hermit crabs (Paguridae; 38.4%W) and all other crabs combined (35.4%W). Hermit crabs were also numerically important (23.9%N) and occurred frequently among the Yellow Irish Lords examined (72.5%FO). Chionoecetes was also numerically important (18.9%N). In the Aleutian Islands region, hermit crabs were less important (9.0%W), but all other crabs (32.6%W) and potentially more-mobile prey (27.9%W) such as squid, octopus and fishes, dominated the diet. Small crustaceans, including isopods, amphipods, and shrimp, comprised a greater fraction of the diet in the Aleutian Islands (12.2%W, 64.9%N) than in the eastern Bering Sea (0.9%W, 7.5%N). Less-mobile and scavenged prey were similarly important in the 2 regions, contributing 12.5%W and 13.8%W to the diets, respectively, in the eastern Bering Sea and the Aleutian Islands regions.

Changes in the diet composition with increasing size of Yellow Irish Lords differed between the eastern Bering Sea and the Aleutian Islands (Fig. 3). Although an important diet component for all sizes of Yellow Irish Lords in the eastern Bering Sea, hermit crabs decreased in importance with increasing predator size. As a group, other crabs increased in importance with increasing size of Yellow Irish Lords, but clear trends in %W were not apparent for the important prey taxa within this group composed of lyre crabs (Hyas spp.), Chionoecetes, and Horsehair Crabs (Erimacrus isenbeckii). However, the maximum size of Chionoecetes consumed by Yellow Irish Lords increased with predator size (Fig. 4). In Aleutian Island waters, prey groups that appeared to decrease in importance included worms (for example, polychaetes, Echiura) and small crustaceans (for example, amphipods and shrimp). Other crabs were most important to intermediate-sized Yellow Irish Lords, and as a group, swimming prey (fishes and cephalopods) increased rapidly in importance for the 2 largest length classes.

DISCUSSION

Parameters of the von Bertalanffy growth model suggest some regional variation in growth between eastern Bering Sea and Aleutian Islands Yellow Irish Lords. Our results show that Yellow Irish Lords in the eastern Bering Sea reach their asymptotic maximum length at a younger age than those found in the Aleutian Islands. This observation could be related to differences in environmental conditions between the 2 regions, such as latitude and temperature. Predation effects and prey field availability are also important considerations. Longevity of this species appears to be similar between the 2 regions, with maximum ages approaching 30 y (Hutchinson and TenBrink 2011). This is in contrast to a reported maximum age of 13 y off Kamchatka (Tokranov 1986).

Our study indicates that the reproductive biology of Yellow Irish Lords in Alaska exhibits similarities and differences between regions. Yellow Irish Lords release 1 batch of eggs annually in a group-synchronous mode of development in the summer in the eastern Bering Sea and Aleutian Islands. This type of development has also been reported by Tokranov (1986), who observed an August to September peak spawning period in Kamchatka waters in the western North Pacific. In the Gulf of Alaska, Rogers and others (1980) observed spawning females in June and August. The fecundity of Yellow Irish Lords from the Aleutian Islands reported in this study is the highest of any species of Hemilepidotus, with the maximum value being approximately 390,000 in a 50-cm female. Tokranov (1988) reported a mean absolute fecundity value of 101,000 oocytes and a maximum of 241,000 oocytes in specimens collected off the coast of Kamchatka for fish ranging in size from 30 to 50 cm. Yellow Irish Lords appear to be more fecund in the Aleutian Islands, but the mechanisms behind this difference are not yet understood.

The Yellow Irish Lord is a benthic predator that consumes a wide variety of prey but appears to favor benthic crustaceans, particularly abundant crab species. The diet composition found in the eastern Bering Sea is generally consistent with other studies. In the eastern Bering Sea, Walleye Pollock (Theragra chalcogramma) and Chionoecetes crabs were the main prey items, with minor contributions from polychaete worms, shrimps, and other crabs (Mito 1974; Brodeur and Livingston 1988). Similarly, Hosoki (1978) examined the diet of Yellow Irish Lords from the eastern Bering Sea and found hermit crabs, Chionoecetes, and other crabs to be dominant prey, followed by amphipods, Walleye Pollock, other gadids, and other fishes. Brodeur and Livingston (1988) reported on the stomach contents of Yellow Irish Lords caught in the eastern Bering Sea, but the majority were sampled during autumn months. They also found hermit crabs, Chionoecetes crabs, and fishes occurred most frequently and comprised the majority of the diet weight, but unlike the other studies, fishery offal was a notable diet component. This result could be because most of the samples were collected during fishery operations in the vicinity of processing vessels where fishery offal is produced, rather than during fishery-independent resource surveys. Opportunistic feeding is also demonstrated on spawning grounds in the western North Pacific, where egg masses of hexagrammids and species of Hemilepidotus are a major component of the diet in late summer (Zolotov and Tokranov 1991). In the Gulf of Alaska, Jewett and Powell (1979) reportedly found majid crabs, gammarid amphipods, and mollusks to be dominant prey. Yang and others (2006) identified Tanner Crab as the most important prey in 3 Yellow Irish Lords.

The diet of Yellow Irish Lords in the Aleutian Islands exhibited some differences from the reported diet in other areas, probably reflecting a difference in relative abundance of the potential prey types. We found fishes, particularly Atka Mackerel (Pleurogrammus monopterygius) and snailfishes (Liparidae) to be more important, and hermit crabs and Horsehair Crabs (Erimacrus isenbeckii) to be less important in the Aleutian Islands than in the eastern Bering Sea. The largest individuals appear to have more opportunities for piscivory in the Aleutian Islands. The greater complexity and variety of habitat around the Aleutian Islands may afford more opportunities for successful ambush predation on mobile fishes and squid than on the broad, relatively flat continental shelf of the eastern Bering Sea. Chionoecetes crabs frequent open mud and sand bottoms (Lauth and Acuna 2007), which are more common in the eastern Bering Sea.

The composition of the Yellow Irish Lord diet changes with size. The trends we found have both similarities and differences with the trends found in Russian waters examined over a similar range of predator sizes: echiurans and Snow Crabs increased in importance, and other decapods, polychaete worms, amphipods, and mollusks decreased in importance with increasing Yellow Irish Lord size (Tokranov 1985). Polychaete worms exhibited no size-related trend in dietary importance in the eastern Bering Sea; in the Aleutian Islands, however, there was a clear decrease in dietary importance that is consistent with the trend in Russian waters. Chionoecetes crabs were important to all sizes of Yellow Irish Lords examined in the eastern Bering Sea, but if individuals smaller than about 15-mm carapace width were not available, then a trend similar to that in Russian waters would result. We found that small crustaceans (mostly isopods, amphipods, and shrimp) decreased in importance with predator size in the Aleutian Islands, similar to the dietary trend for amphipods in Russian waters, but small crustaceans contributed little to the diet of Yellow Irish Lords at any size we sampled in the eastern Bering Sea. We also found no trend in the dietary importance of Echiura with predator size in the eastern Bering Sea or the Aleutian Islands.

The general life-history pattern of the Yellow Irish Lord, using results from this study and others, suggests that this species follows an intermediate strategy (Winemiller 1989; King and McFarlane 2003), with characteristics that are generally in the mid-range of "r- and K-selected" attributes. Results here suggest at least some regional variation in life-history parameters may exist. It is possible that life-history variation described here may be the result of phenotypic expression influenced by local environment, habitat, and available prey. Yellow Irish Lords are benthic predators that consume locally abundant prey. The eastern Bering Sea continental shelf has more benthic influence on its food web and energy flow relative to the Aleutian Islands ecosystem, which is dominated by pelagic species such as Atka Mackerel and Pacific Ocean Perch (Sebastes alutus; Aydin and others 2006). Life-history variation within a region may also exist. For example, the biology of Yellow Irish Lords along the extent of the Aleutian Islands could be influenced by major biophysical transition zones (for example, Samalga Pass) that affect nutrient levels and primary production (Ladd and others 2005). Further work on a larger scale will be needed to determine if within-region differences exist.

Our study provides baseline and updated information for identifying and understanding variation in the life history and food habits of the Yellow Irish Lord, which will provide a scientific foundation for developing management strategies for this species in the eastern Bering Sea and Aleutian Islands. There currently is no specific federal management plan for individual sculpin species in Alaskan waters. All sculpins are managed together as regional complexes, including in the Bering Sea-Aleutian Islands (BSAI) management region, although these 2 areas within this region are dramatically different habitats, and species within these complexes may have different life-history traits. Given the observed differences in some life-history traits of the Yellow Irish Lord in this study among contrasting environments within the BSAI, fisheries managers should consider this information when making future management decisions.

ACKNOWLEDGMENTS

We thank the AFSC scientists aboard the fishing vessels Sea Storm, Arcturus, Aldebaran, and Northwest Explorer for sample collection during the eastern Bering Sea and Aleutian Islands bottom trawl surveys. We also thank the following AFSC personnel for support: R Hipbshipman and A Whitehouse for stomach analysis; J Berger for observer logistics, and D Nichol, S McDermott, G Lang, M Wilkins and 2 reviewers for comments that improved this manuscript. The findings and conclusions in the paper are those of the authors and do not necessarily represent the views of the National Marine Fisheries Service, NOAA. This research was primarily funded by the North Pacific Research Board (Project 628).

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Submitted 15 October 2012, accepted 10 January 2013. Corresponding Editor: James W Orr.

TODD T TENBRINK AND TROY W BUCKLEY

Resource Ecology and Fisheries Management Division, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way NE, Seattle, WA 98115

TABLE 1. Number of samples collected and analyzed by area and year.

Region          Year   Month       Lengths

E. Bering Sea   1994   June              10
                2005   June             395
                2005   July             209
                2006   June             266
                2006   July             226
                2007   June              37
                2007   July             235
                2007   October            3
                2008   February          21
                2008   March              8
                2008   September         51
Aleutian Is.    2005   August             6
                2006   June             663
                2006   July             329
                2006   August           107
                2007   October            5

Region          Year   Otoliths   Ovaries   Stomachs

E. Bering Sea   1994                           10
                2005     117
                2005     105                   9
                2006     103        43         57
                2006      66        36         26
                2007                11         18
                2007                15         35
                2007                 3
                2008                21
                2008                 8
                2008                51
Aleutian Is.    2005                 6
                2006     187        71         65
                2006     194        113        91
                2006      17                   5
                2007                 5

TABLE 2. Estimates of the von Bertalanffy growth parameters
for Yellow Irish Lord (Hemilepidotus jordani) in the eastern
Bering Sea (2005-2006, pooled) and Aleutian Islands (2006).
[r.sup.2] is the coefficient of determination; n is the
sample size. Asymptotic standard errors ([s.sub.x])
are shown  in parentheses below each estimate.

                            Eastern Bering Sea

                        Combined    Males    Females

[L.sub.[varies]] (cm)     43.0      46.8      42.1
[S.sub.[bar.x]]          (4.28)    (10.86)   (4.35)

k                        0.299      0.257     0.295
[S.sub.[bar.x]]         (0.018)    (0.029)   (0.019)

[t.sub.0]                0.056     -0.071    -0.022
[S.sub.[bar.x]]         (0.172)    (0.311)   (0.198)

[r.sup.2]                 0.80      0.81      0.83
n                         386        140       246

                              Aleutian Islands

                        Combined    Males    Females

[L.sub.[varies]] (cm)     45.8      52.2      44.2
[S.sub.[bar.x]]          (6.99)    (16.99)    (7.60

k                        0.179      0.147     0.171
[S.sub.[bar.x]]         (0.013)    (0.018)   (0.015)

[t.sub.0]                -0.808    -0.851    -1.258
[S.sub.[bar.x]]         (0.291)    (0.429)   (0.393)

[r.sup.2]                 0.78      0.84      0.80
n                         398        160       238

TABLE 3. Percent frequency of occurrence (%FO), percent total
number (%N), and percent total weight (%W) of prey taxa
in the diets of Yellow Irish Lord (Hemilepidotus jordani)
sampled from the eastern Bering Sea and Aleutian Islands
with at least 2%FO, 1%N, or 1%W in one of the regions.

                                         Eastern Bering Sea

Prey taxa                                 %FO     %N      %W

Hydroida (hydroid)                       0.67    0.57    0.02
Polychaeta (polychaete)                  17.45   2.55    1.26
Polynoidae (polychaete)                  36.24   11.35   1.22
Phyllodocidae (polychaete)               16.78   2.93    0.34
Nereidae (polychaete)
Onuphidae (polychaete)                   1.34    0.19    0.05
Eunicidae (polychaete)
Lumbrineridae (polychaete)
Mollusca                                 5.37    0.85    2.00
Gastropoda (snail)                       7.38    1.32    2.33
Lamellariidae (snail)
Nudibranchia (sea slug)                  0.67    0.38    0.09
Bivalvia (clam)                          13.42   2.93    3.83
Cephalopoda (squid and octopus)          1.34    0.19    2.31
Teuthida (squid)
Octopoda (octopus)
Crustacea
Isopoda (isopod)                         2.68    0.38    0.08
Arcturidae (isopod)
Gammaridea (amphipod)                    7.38    3.97    0.36
Ampeliscidae (amphipod)
Caprellidea (amphipod)                   3.36    2.18    0.09
Natantia (shrimp)                        2.01    0.28    0.03
Caridea (shrimp)                         1.34    0.19    0.03
Hippolytidae (shrimp)                    2.01    0.38    0.12
Pandalus sp. (shrimp)
Crangonidae (shrimp)                     0.67    0.09    0.03
Reptantia (crab)                         6.04    1.14    1.48
Anomura (crab)                           2.01    0.28    0.36
Anomura (crab)
Paguridae (hermit crab)                  72.48   23.94   38.09
Elassochirus tenuimanus
Elassochirus cavimanus
Majidae (spider crab)                    5.37    0.85    0.85
Oregonia sp.                             2.68    0.47    0.17
Oregonia gracilis                        2.68    0.38    0.68
Hyas sp.                                 16.11   4.26    4.11
Hyas lyratus                             1.34    0.28    1.69
Hyas coarctatus                          5.37    1.14    2.78
Chionoecetes spp.                        19.46   10.97   3.60
Chionoecetes opilio (Snow Crab)          4.70    1.42    1.36
Chionoecetes bairdi (Tanner Crab)        19.46   6.53    6.31
Erimacrus isenbeckii (Horsehair Crab)    11.41   2.84    9.72
Cancer oregonensis                       2.68    0.76    1.76
Echiura (marine worm)                    14.77   5.01    4.10
Ectoprocta (bryozoan)
Ophiurida (brittle star)                 4.03    0.85    0.84
Ophiuridae (brittle star)                2.01    0.66    0.24
Holothuroidea (sea cucumber)             1.34    0.28    0.16
Teleostei (fish)                         3.36    0.47    0.03
Non-gadoid fish remains                  2.68    0.66    0.71
Pleurogrammus monopterygius
(Atka Mackerel)
Liparidae (snailfish)
Unidentified eggs                        0.67    0.09    2.25
Fishery offal                            2.01    0.28    1.05
Total sample size                         155
Total empty                                6
Total prey number                                1,556
Total prey weight (g)                                    1482

                                          Aleutian Islands

Prey taxa                                 %FO     %N      % W

Hydroida (hydroid)                       5.77    0.31    0.83
Polychaeta (polychaete)                  40.38   8.64    2.82
Polynoidae (polychaete)                  22.44   2.74    0.62
Phyllodocidae (polychaete)               19.23   2.62    0.82
Nereidae (polychaete)                    5.13    0.31    0.03
Onuphidae (polychaete)                   3.21    0.23    0.07
Eunicidae (polychaete)                   4.49    0.51    0.80
Lumbrineridae (polychaete)               3.21    0.74    0.38
Mollusca                                 2.56    0.23    0.40
Gastropoda (snail)                       11.54   1.56    2.36
Lamellariidae (snail)                    3.21    0.43    0.13
Nudibranchia (sea slug)                  0.64    0.08    1.48
Bivalvia (clam)                          2.56    0.16    0.15
Cephalopoda (squid and octopus)          1.28    0.20    0.09
Teuthida (squid)                         1.28    0.08    2.38
Octopoda (octopus)                       4.49    0.27    0.38
Crustacea                                4.49    0.35    0.23
Isopoda (isopod)                         16.67   17.04   2.80
Arcturidae (isopod)                      12.82   9.03    2.24
Gammaridea (amphipod)                    48.72   27.47   2.59
Ampeliscidae (amphipod)                  2.56    0.23    0.02
Caprellidea (amphipod)                   23.08   8.05    0.37
Natantia (shrimp)                        4.49    0.31    0.06
Caridea (shrimp)                         12.82   1.41    1.20
Hippolytidae (shrimp)                    7.05    0.55    0.95
Pandalus sp. (shrimp)                    3.85    0.27    0.82
Crangonidae (shrimp)                     3.21    0.20    0.32
Reptantia (crab)                         7.05    0.43    1.27
Anomura (crab)
Anomura (crab)
Paguridae (hermit crab)                  23.08   1.68    3.68
Elassochirus tenuimanus                  4.49    0.27    1.31
Elassochirus cavimanus                   6.41    0.47    3.25
Majidae (spider crab)                    6.41    0.51    2.00
Oregonia sp.                             12.82   1.41    5.70
Oregonia gracilis                        19.23   2.58    11.85
Hyas sp.                                 1.92    0.27    2.02
Hyas lyratus                             6.41    0.66    4.58
Hyas coarctatus
Chionoecetes spp.
Chionoecetes opilio (Snow Crab)
Chionoecetes bairdi (Tanner Crab)
Erimacrus isenbeckii (Horsehair Crab)    1.28    0.08    1.63
Cancer oregonensis                       4.49    1.13    2.58
Echiura (marine worm)                    0.64    0.08    0.04
Ectoprocta (bryozoan)                    3.85    0.23    0.02
Ophiurida (brittle star)                 3.21    0.23    0.09
Ophiuridae (brittle star)                12.82   1.99    2.38
Holothuroidea (sea cucumber)             4.49    0.31    2.97
Teleostei (fish)                         5.77    0.35    0.18
Non-gadoid fish remains                  7.69    0.51    1.71
Pleurogrammus monopterygius
(Atka Mackerel)                          2.56    0.16    17.39
Liparidae (snailfish)                    1.28    0.08    5.25
Unidentified eggs
Fishery offal                            1.28    0.04    1.78
Total sample size                         161
Total empty                                5
Total prey number                                2,559
Total prey weight (g)                                    1284
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Article Details
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Author:TenBrink, Todd T.; Buckley, Troy W.
Publication:Northwestern Naturalist: A Journal of Vertebrate Biology
Article Type:Report
Geographic Code:1USA
Date:Sep 22, 2013
Words:5784
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