Progress in Oceanography 136 (2015) 115–132
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Progress in Oceanography
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Fish communities across a spectrum of habitats in the western Beaufort Sea and Chukchi Sea ⇑ E. Logerwell a, , M. Busby a, C. Carothers b, S. Cotton b, J. Duffy-Anderson a, E. Farley c, P. Goddard a, R. Heintz c, B. Holladay b, J. Horne a,d, S. Johnson c, B. Lauth a, L. Moulton e, D. Neff c, B. Norcross b, S. Parker-Stetter d,f, J. Seigle g, T. Sformo h a NOAA/NMFS, Alaska Fisheries Science Center, 7600 Sand Point Way, N.E., Seattle, WA 98115, United States b School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 905 N. Koyukuk Dr., Fairbanks, AK 99775, United States c NOAA/NMFS, Alaska Fisheries Science Center, Auke Bay Laboratory, Ted Stevens Marine Research Institute, 17109 Pt. Lena Loop Rd., Juneau, AK 99801, United States d School of Aquatic and Fisheries Science, University of Washington, Box 355020, Seattle, WA 98105, United States e MJM Research, LLC, 1012 Shoreland Drive, Lopez Islands, WA 98261, United States f NOAA/NMFS, Northwest Fisheries Science Center, 2725 Montlake Blvd., Seattle, WA 98112, United States g ABR, Inc. – Environmental Research & Services, P.O. Box 240268, Anchorage, AK 99524, United States h North Slope Borough Department of Wildlife Management, P.O. Box 69, Barrow, AK 99723, United States article info abstract
Article history: The increased scientific interest in the Arctic due to climate change and potential oil and gas development Available online 12 May 2015 has resulted in numerous surveys of Arctic marine fish communities since the mid-2000s. Surveys have been conducted in nearly all Arctic marine fish habitats: from lagoons, beaches and across the continental shelf and slope. This provides an opportunity only recently available to study Arctic fish communities across a spectrum of habitats. We examined fish survey data from lagoon, beach, nearshore benthic, shelf pelagic and shelf benthic habitats in the western Beaufort Sea and Chukchi Sea. Specifically, we compare and contrast relative fish abundance and length (a proxy for age) among habitats and seas. We also exam- ined ichthyoplankton presence/absence and abundance of dominant taxa in the shelf habitat. Our synthe- sis revealed more similarities than differences between the two seas. For example, our results show that the nearshore habitat is utilized by forage fish across age classes, and is also a nursery area for other spe- cies. Our results also indicated that some species may be expanding their range to the north, for example, Chinook Salmon. In addition, we documented the presence of commercially important taxa such as Walleye Pollock and flatfishes (Pleuronectidae). Our synthesis of information on relative abundance and age allowed us to propose detailed conceptual models for the life history distribution of key gadids in Arctic food webs: Arctic and Saffron Cod. Finally, we identify research gaps, such as the need for sur- veys of the surface waters of the Beaufort Sea, surveys of the lagoons of the Chukchi Sea, and winter sea- son surveys in all areas. We recommend field studies on fish life history that sample multiple age classes in multiple habitats throughout the year to confirm, resolve and interpret the patterns in fish habitat use that we observed. Published by Elsevier Ltd.
1. Introduction a key role in the Arctic, as they do in many systems, as prey to sea- birds, marine mammals and humans (Bradstreet et al., 1986; There are 242 currently known species of benthic and pelagic Whitehouse et al., 2014). They are also potentially important con- fishes in Arctic marine waters, distributed among 45 families sumers of secondary production in the Arctic in both benthic and (Mecklenburg et al., 2010). Fish such as Arctic Cod (Boreogadus pelagic zones (Frost and Lowry, 1981, 1983; Jarvela and saida), salmon and forage fishes (e.g., Capelin Mallotus villosus) play Thorsteinson, 1999). A synthesis of current fish community
⇑ Corresponding author. E-mail addresses: [email protected] (E. Logerwell), [email protected] (M. Busby), [email protected] (C. Carothers), [email protected] (S. Cotton), [email protected] (J. Duffy-Anderson), [email protected] (E. Farley), [email protected] (P. Goddard), [email protected] (R. Heintz), [email protected] (B. Holladay), [email protected] (J. Horne), [email protected] (S. Johnson), [email protected] (B. Lauth), [email protected] (L. Moulton), [email protected] (D. Neff), [email protected] (B. Norcross), [email protected] (S. Parker-Stetter), [email protected] (J. Seigle), todd. [email protected] (T. Sformo). http://dx.doi.org/10.1016/j.pocean.2015.05.013 0079-6611/Published by Elsevier Ltd. 116 E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 composition and habitat use supports the goals of SOAR by provid- the first recent historical low in summer sea ice (NCAR, 2007) ing a baseline against which to measure future change. In addition, and can be considered the start of the ‘‘new normal’’ in Arctic it provides insight into how climate change might impact Arctic climate and ocean conditions (Jeffries et al., 2013). fish communities and the predators that depend on them via We synthesized data from fish surveys of several habitats in the changes to their habitat. western Beaufort and Chukchi Seas: coastal lagoon, beach (waters Surveys have been conducted in nearly all Arctic marine fish <5 m deep), nearshore benthic (waters <10 m deep), shelf (>20 m habitats during the past decade: from coastal lagoons out to the deep) surface, shelf midwater (pelagic habitat below the surface continental slope. The shallow lagoons inshore of barrier islands and above the bottom) and shelf benthic. We did not have data of the Beaufort Sea are characterized in the ice-free season by for the central and eastern Beaufort Sea. We also examine ichthy- brackish and relatively warm water. This water is formed during oplankton data from shelf surveys from both seas. Table 1 summa- spring when floodwaters from North Slope rivers flow to sea and rizes the years, months and habitats for which we had survey data, mix with marine waters (Craig, 1984). The nearshore zone is a and Fig. 1 shows the locations of all stations (subsequent figures transition between estuarine waters originating from lagoons and will show which surveys sampled at which stations). Data were marine waters offshore. The extent of the band of estuarine water collected from as early as June to as late as October. There were in the nearshore depends on the amount of freshwater input, near- no data from the shelf surface of the Beaufort Sea, nor from the shore currents and prevailing winds. By the end of winter the shal- lagoon and shelf midwater of the Chukchi Sea. Fish caught were low waters of lagoons and the nearshore are frozen solid. Lagoon often identified to species, but not always, so catch by family is habitat is less prevalent in the Chukchi Sea and less well-studied, reported in some cases. Catch-per-unit effort (CPUE), a measure but presumably the lagoons and nearshore habitats in the of fish density, was used to represent relative fish abundance for Chukchi have similar characteristics as those observed in the each habitat. In addition individual length data were summarized Beaufort. Beaches in the Beaufort and Chukchi Seas are rarely steep for each species or taxonomic group (average and min–max). and rocky, but instead are typically sand, gravel, mud or some Virtually no fish age data were available from the surveys, so fish combination of these (https://alaskafisheries.noaa.gov/shorezone/). age ranges were based on age-length relationships from other The shallow (50 m) and wide Chukchi Sea shelf extends areas (predominantly Alaska region). Finally, three diversity 800 km northward from Bering Strait to the shelfbreak. Water indices were calculated for each habitat in each Sea: Richness (S), flows north through Bering Strait, bringing heat, nutrients, carbon Simpson’s Index (D) and Shannon Index (H) (Begon et al., 1990). and organisms that strongly influence the characteristics of the Because of the different levels of taxonomic resolution in the data- Chukchi Sea ecosystem (Weingartner, 2008). The Alaskan sets, diversity indices were calculated at the level of Family. Maps Beaufort Sea shelf is narrower than the Chukchi Sea shelf of survey stations were created in ESRI ArcMap 10.0, using Albers (80 km wide) and relatively flat; bottom depths increase gradu- projection and the North American Datum 1983. ally from the coast to the 80 m isobath and then drop off rapidly along the shelfbreak and slope. Oceanographic characteristics of the Beaufort Sea are influenced by water flowing eastward from 2.1. Beaufort Sea the Chukchi Sea, from the westward flowing southern limb of the Beaufort Gyre and discharge from the Mackenzie River We synthesized data from fish surveys conducted in five differ- (Weingartner, 2008). ent habitats in the western Beaufort Sea: lagoon, beach, nearshore Increased scientific interest in the Arctic due to climate change, benthic, shelf midwater and shelf benthic. Data were collected potential oil and gas development and the International Polar Year from June through September (depending on the survey). (IPY 2007–2009) has resulted in the surveys of Arctic fish commu- The lagoon habitat of the Beaufort Sea was sampled with two nities synthesized here. There was a period of large-scale Arctic net types, fyke nets and gill nets. The purpose of these on-going surveys in the early 1970s to the early 1990s when there was a surveys is to investigate the subsistence fishery in Elson Lagoon, concerted effort to study areas of potential oil and gas develop- an important resource for the community of Barrow (Bacon et al., ment, the Outer Continental Shelf Environmental Assessment 2009). Fyke nets were maintained by scientists from the North Program (OCSEAP, 1990). There has been a gap in large-scale Slope Borough Department of Wildlife Management to estimate Arctic research since the OCSEAP era until the 2000s. Our surveys species present, size and age distribution and health status of fish. from 2007 to the present provide an opportunity only recently In addition, daily gill net surveys of subsistence fishermen are available to study Arctic fish communities across a spectrum of conducted (http://www.north-slope.org/departments/wildlife- habitats. This project was a collaboration among researchers at a management/studies-and-research-projects/fish/fish-surveys). The number of agencies, local and federal, and universities providing fyke net had a minimum mesh size of 6.4 mm and was deployed data in a cooperative fashion from their individual surveys. We at several locations within the Elson Lagoon system compare the fish community composition in lagoon, beach, near- (Figs. 2 and 3). The net was fixed in place and left open to fish for shore benthic, shelf pelagic and shelf benthic habitats. We also 24 h and sampled each day (with the exception of weekends or use information on age-class of fish along with ichthyoplankton before storms) between the months of June and August. Data from data to compare and contrast how different taxa use these habitats 2009–2012 were used for this analysis (Moulton and Seigle, 2012). throughout their life history. Finally, we explore similarities and Catch-per-unit-effort (CPUE) was calculated as No. fish/effort hours, differences in community composition and habitat use of where No. fish was the total number of fish caught in a year and Beaufort and Chukchi Sea fishes. Our synthesis provides a baseline effort hours was the total number of hours the net was open in a for climate change impacts in the future and suggests directions for year. Total effort hours from 2009–2012 was 2304. The lagoon gill future research. net data were from the 2011 subsistence gill net fishery from the months of June–September. The purpose of the gill net study was to gather information on salmon use, abundance and distribution 2. Methods in the Arctic (Cotton, 2012). Gill nets were deployed by fishermen at several locations spanning the west to east range of the fyke The temporal scope of our synthesis is the ice-free spring to fall net locations (Fig. 3). The mesh size of the gill nets used in the fish- season and the years 2007–2012. These years represent our best ery ranged from 64 to 203 mm. Catches were from daily net obser- available data coverage across habitats. In addition, 2007 marks vations and fisher’s logbook data of recorded catches. Daily CPUE E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 117
was calculated by dividing No. fish by effort, which was the number of hours the net was fished standardized to a common net length (60 feet). The total number of hours all nets were fished in 2011 was 20,072. The average of daily CPUE was then calculated. The beach and nearshore benthic habitat was sampled as part of a study to update information on fishes of coastal waters of the Sept Aug–Sept Alaskan Arctic (Johnson et al., 2010). Fish were captured with a beach seine and bottom trawl on the seaward side of Cooper Island (Figs. 2 and 3). The beach seine stations were in water <5 m deep and were <20 m from shore. The net was a 37 m long variable mesh beach seine with 3.2 mm square mesh in the bunt and was set as a ‘‘round haul’’ (National Marine Fisheries Service
water Shelf benthic Ichthyo-plankton (NMFS), 2010). Offshore of each beach seine station, fish were cap- tured with a bottom trawl at two depths: 5 m (about 1.0 km off- shore) and 8 m (about 2.5 km offshore). The trawl mouth was 2.6 m wide and 1.2 m deep, the trawl total length was 5.2 m, and the codend was made of 3.2 mm stretch mesh. The trawl was towed from a skiff at about 2.5 knots. Three stations were sampled with beach seines in August 2007 and September 2009. One haul
Aug–Sept Aug–Sept was made at each station. CPUE was No. fish per haul and mean CPUE was calculated for each sampling period (n = 3 hauls). Three stations, each with two depths, were sampled with the bot- tom trawl in August 2007 and 2009 and September 2009. CPUE was No. fish per haul and mean CPUE was calculated for each sam- pling period (n = 6 hauls). The shelf midwater and benthic habitats were sampled as part of an August 2008 survey of the Beaufort Sea, the goal of which was to provide baseline information on areas of potential oil and gas development (Logerwell et al., 2010; Rand and Logerwell, 2010; Aug–Sept Aug–SeptAug–Sept Aug–Sept Aug–Sept Aug–Sept Sept July–Oct Sept Parker-Stetter et al., 2011). The midwater was sampled with a Marinovich trawl net as part of an acoustic survey (Parker-Stetter
Chukchi Sea et al., 2011), so the net was deployed to identify constituents of the backscatter across the study area (Fig. 2). Net depth ranged from 15 m to 320 m (maximum depth was 10 m off bottom). The fishing dimensions of the Marinovich net were 3–4 m vertical and 6 m horizontal and the mesh of the codend liner was 12 mm. Vessel speed was maintained at 2–4 knots while towing the net. Net position and headrope height were monitored in real-time during the deployment. CPUE was calculated as No. fish per minute (haul duration) and averaged over all hauls (n = 28 hauls). The shelf benthic habitat was sampled with an 83-112 Eastern otter trawl deployed on a depth-stratified grid of stations. Positions were modified from a regular grid by the presence of ice and untrawl- able bottom (Fig. 2). The net had a 25.3 m headrope, a 34.1 m foo- trope and had a 38 mm mesh liner throughout the body and codend. The net was towed at a vessel speed around 3 knots. Net height and width were measured and monitored in real time with acoustic net mensuration equipment and trawl foot rope contact with the seafloor was monitored using a bottom contact sensor. These data were used to estimate area swept by the net. CPUE was calculated as No. fish per area swept and averaged over all hauls (n = 11 hauls). An ichthyoplankton survey was also part of the August 2008 study (Logerwell et al., 2010). A MARMAP 60 cm bongo net fitted with 0.505 mm mesh nets was deployed at oceanographic sam- pling stations across the range of depths (Fig. 2). The net was towed double-oblique from the surface down to a depth 10 m off bottom and back to the surface. Ichthyoplankton density was cal- culated as No./10 m2 and then averaged over all stations (n =28 stations).
Lagoon Beach Nearshore benthic Shelf surface Shelf midwater Shelf benthic Ichthyo-plankton Lagoon Beach Nearshore benthic Shelf surface Shelf mid 2.2. Chukchi Sea 200720082009 July–Sept2010 Aug July–Sept 2011 July–Sept Aug Sept 2012 July–Sept Aug Aug Aug Aug Aug–Sept Aug–Sept July Year Beaufort Sea We synthesized data from fish surveys conducted in five differ- Table 1 Years, months and habitats for which fish and ichthyoplankton survey data were available for the synthesis, for the Beaufort and Chukchi Seas. ent habitats in the Chukchi Sea: beach, nearshore benthic, shelf 118 E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132
Fig. 1. Stations sampled by fish and ichthyoplankton surveys of the Beaufort and Chukchi Seas, 2007–2012 (total number of stations = 467). Dashed line indicates longitudinal boundary between Beaufort and Chukchi Seas.
Fig. 2. Beaufort Sea study area. Stations sampled in the lagoon (fyke net), beach (seine), nearshore benthic (bottom trawl), shelf benthic (bottom trawl), and shelf midwater (trawl). Stations sampled by ichthyoplankton survey are also shown. E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 119
Fig. 3. Detail of lagoon and nearshore study areas of the Beaufort Sea. Stations sampled by the fyke net, beach seine and nearshore bottom trawl are shown. Gill nets were set near the most northern fyke net and spanning the shore westward towards the other fuke net locations shown in Elson Lagoon (indicated by shaded area).
surface, shelf midwater and shelf benthic. Data were collected from spacing was 36–55 km. 25 stations were sampled in September July through September (depending on the survey). 2007 and 81 were sampled in August-September 2012 (Fig. 4). The beach and nearshore benthic habitats were sampled as part Pelagic fish were captured with a Cantrawl 300 midwater trawl of the Coastal Assessments research program of NOAA Alaska with a mean horizontal spread of 54 m, mesh size of 12 mm, rigged Fisheries Science Center Auke Bay Laboratory (http://www.afsc. to sample the top 12 m of the water column. CPUE was No. noaa.gov/ABL/Habitat/ablhab_coastal.htm). Fish were captured fish/km2 and mean CPUE was calculated for each survey. with a beach seine and bottom trawl on the coast near Barrow The shelf benthic habitat was sampled with a large bottom (Figs. 4 and 5). The gear and deployment methods were the same trawl as part of the Arctic EIS. Sampling design was based on a as those used to survey the Beaufort beach and nearshore habitats 55.6 km (30 nmi) square grid pattern with the trawl stations (Thedinga et al., 2013). The beach seine stations were in water located at the approximate center of each grid cell, resulting in a <5 m deep. Offshore of each beach seine station, fish were captured total of 71 sampling locations (Fig. 4). The survey was conducted with a bottom trawl at two depths: 5 m and 8 m. Six stations were during August-September 2012. The bottom trawl was an 83-112 sampled with beach seines in August 2007–2009 and September Eastern otter trawl, the same net used to sample the Beaufort shelf 2009. One haul was made at each station. CPUE was No. fish per benthic habitat. The codend of the net had a liner of 3.2 cm mesh. haul and mean CPUE was calculated for each sampling period CPUE was calculated as No. fish/area swept (ha; derived from net (n = 6 hauls). Six stations, each with two depths, were sampled mensuration data) and averaged over all hauls. with the bottom trawl in August 2007–2009 and September The shelf benthic habitat was also sampled with a smaller net, 2009. CPUE was No. fish per haul and mean CPUE was calculated the 3 m plumb-staff beam trawl (Gunderson and Ellis, 1986). for each sampling period (n = 12 hauls). This gear was deployed at stations throughout the Chukchi Sea The shelf surface waters were sampled as part of the Bering over the course of seven multi-disciplinary surveys (Fig. 6). Sea-Aleutian Salmon International Survey (BASIS; http://www. Table 2 provides a summary of the years, months, vessel/cruise npafc.org/science_basis.html) and the Arctic Ecosystem name and acronym, and number of stations sampled for each sur- Integrated Survey (EIS; https://web.sfos.uaf.edu/wordpress/arcti- vey. Stations were selected by two methods, coincident with other ceis/). BASIS was a coordinated program of cooperative research disciplines (2009-RUSALCA and two CSESP surveys), or opportunis- on Pacific salmon in the Bering Sea designed to investigate the tic samples when time was made available by the host cruise, usu- response of salmon to climate change. The survey typically ally at night or along a set cruise track (BASIS, COMIDA, 2007 extended from the Alaska Peninsula to just north of St. Lawrence Oshoro Maru and 2008 Oshoro Maru). During all surveys, a 3 m Island, but in 2007 it included the Bering Strait and northeastern plumb staff beam trawl with a 4 mm mesh codend liner and an Chukchi Sea. Arctic EIS was a multi-disciplinary study of the effective mouth opening of 2.26 width and 1.2 m height was used oceanography, lower trophic levels, crab and fish communities of to collect benthic fishes. The net was towed at 1–1.5 knots on the the northeastern Bering Sea and eastern Chukchi Sea. Station bottom for 2–5 minutes, typically, and distance was calculated 120 E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132
Fig. 4. Chukchi Sea study area. Stations sampling the nearshore (nearshore bottom trawl and beach seine), shelf benthic (bottom trawl), and shelf surface (trawl) are shown.
Fig. 5. Detail of the nearshore study area of the Chukchi Sea. Stations sampled by beach seine and nearshore bottom trawl are shown. E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 121
Fig. 6. Chukchi Sea study area. Stations sampled by plumb staff beam trawl on several surveys are shown.
Table 2 Table 3 Summary of shelf beam trawl surveys. Summary of ichthyoplankton surveys.
Year Month(s) Vessel/Cruise name No. Year Month(s) Vessel/ Gear No. stations stations Cruise name 2007 September Bering Sea-Aleutian Salmon 27 2007 September BASIS 60-cm bongo 47 International Survey (BASIS)a 2009 September RUSALCA 60-cm bongo 31 2007 August Oshoro Marub 9 2010 August–September CHAOZ 1-m2 epibenthic sled 56 2008 July Oshoro Marub 15 2011 August–September CHAOZ 1-m2 epibenthic sled 84 2009 August August Chukchi Sea 25 Environmental Studies Program (CSESP)c 2009 September–October September CSESPc 26 partial spatial and temporal overlap, the catch compositions 2009 July–August Chukchi Sea Offshore Monitoring 30 among surveys were not dissimilar. The top ten taxa in terms of d in Drilling Area (COMIDA) relative CPUE were similar among all beam trawl surveys, thus 2009 September Russian-American Long-term 21 Census of the Arctic (RUSALCA)e the CPUEs from all surveys were averaged and catch composition was calculated. a http://www.npafc.org/science_basis.html. Ichthyoplankton data were collected during four cruises in the b Norcross et al. (2013a,b). c Day et al. (2013) and Norcross et al. (2013b). Chukchi Sea (Table 3 and Fig. 7). Ichthyoplankton was sampled d http://www.comidacab.org/Default.aspx, Holladay et al. unpublished data. during the 2007 BASIS and 2009 RUSALCA cruises described above e http://www.arctic.noaa.gov/aro/russian-american, Holladay et al. unpublished using a standard MARMAP 60 cm bongo net (Posgay and Marak, data. 1980) fitted with 0.505 mm mesh nets. The net was towed double-obliquely from the surface down to a depth 10 m off bot- tom and back to the surface. Ichthyoplankton was collected during the BOEM Chukchi Acoustics, Oceanography, and Zooplankton between positions of the vessel when towing cable was fully (CHAOZ) surveys in 2010 and 2011 with a 1 m2 epibenthic sled deployed and haul back began. CPUE was No. fish/1000 m2 and trawl (Tabery et al., 1977) fitted with 0.333 mm mesh nets. In mean CPUE was calculated for each survey. 2010, a single net was fitted on the sled and fished obliquely from Fish catch composition for each habitat type was calculated as % the bottom to surface. In 2011, two nets were used with the first CPUE by number averaged over all surveys for that net type/habitat net being fished for approximately 5 minutes with the sled in con- with the exception of the surface trawl surveys. Catch composition tact with the bottom and the second fished obliquely from the bot- for the surface trawl surveys of 2007 and 2012 was very different, tom to surface. Presence/absence of all taxa was tabulated and so data for each year are presented separately. Even though the density (No./10 m2) was calculated for the most abundant taxa. beam trawl surveys conducted in 2007, 2008 and 2009 only had The mean density across surveys was then calculated, with one 122 E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132
Fig. 7. Chukchi Sea study area. Stations sampled by ichthyoplankton nets on several surveys are shown. exception. Because there was virtually no spatial overlap between midwater and benthic. Capelin were found in all habitats and dom- the 2009 and the 2007, 2010 and 2011 surveys, the data from the inated the beach seine catch. 2009 survey were treated separately. Arctic Cod dominated the nearshore bottom trawl, shelf midwa- ter trawl and shelf bottom trawl catch (Table 4). The size range of Arctic Cod in all habitats was similar and fairly broad (26–230 mm; 3. Results and discussion Table 5), and likely spans several age classes from age-0 to age-3 and greater (Norcross et al., 2015). In the three habitats outside 3.1. Beaufort Sea the lagoon, Arctic Cod were largest in the shelf benthic, although smaller (age-0) fish were present on the shelf benthic along with Salmonids (Salmonidae) made up a large portion of the catch in the large fish. Arctic Cod eggs, larvae and juveniles were found in the lagoon, in both the fyke net and gill net surveys (Table 4). The the shelf ichthyoplankton (Table 6). Furthermore, catch density gill net catches were particularly dominated by salmonids, but of Arctic Cod larvae was greatest of all ichthyoplankton taxa these data were from subsistence fishers and were thus biased (Table 7). This suggests that Arctic Cod use the Beaufort Sea shelf because salmonids such as Broad Whitefish (Coregonus nasus) for spawning and larval development, development of age-0 fish and Least Cisco (Coregonus sardinella) were target species. Least occurs throughout the nearshore and shelf and fish move/stay off- Cisco, Chum Salmon (Oncorhynchus keta) and Pink Salmon shore as they age. (Oncorhynchus gorbuscha) dominated the catches. Least Cisco, Saffron Cod (Eleginus gracilis) was present in the lagoon, beach Chum Salmon and Pink Salmon are Arctic residents so this result and nearshore habitats (Table 4). Saffron Cod were also present is expected. However, a few Sockeye Salmon (Oncorhynchus nerka) in the shelf benthic habitat but at low relative CPUE (0.005%). and one Chinook Salmon (Oncorhynchus tshawytscha) also were Saffron Cod were largest in length in the lagoon (74–394 mm; caught. Sockeye Salmon are known to spawn in the Mackenzie Table 5). Results from the ichthyoplankton survey on the shelf River, so the potential for capturing adult Sockeye returning to showed that Saffron Cod were the second most abundant taxa in their natal river is high, however Chinook Salmon have rarely been the catch (Table 7). Length range of Saffron Cod in the nearshore found in the Arctic, so this result is highly unusual (Stephenson, and beach (22–78 mm) indicates these fish were juveniles 2006; Irvine et al., 2009). The size range of the salmonids (426– (Table 5 (Norcross et al., 2015)). These patterns in larval, juvenile 775 mm) indicates that these fishes were immature and maturing and adult distribution suggest that Saffron Cod spawn on the shelf (Table 5; Farley et al., 2009; Moss et al., 2009; E. Farley, unpubl.). and move into nearshore and the lagoon as they age. This hypoth- Forage fishes (Smelts (Osmeridae), Pacific Herring (Clupea pal- esis could be addressed by seasonal sampling of multiple life stages lasii) and Pacific Sand Lance (Ammodytes hexapterus)) seemed to of Saffron Cod, including sampling the surface waters (our surface have a greater tendency to use habitats close to shore (Table 4). trawl data from the Chukchi Sea have shown relatively high densi- The lagoon, beach and nearshore benthic habitats were character- ties of Saffron Cod). In addition, ichthyoplankton sampling in the ized by a greater number of forage fish species than the shelf lagoon would reveal whether they also spawn in that habitat. E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 123
Table 4 Catch composition in the Beaufort Sea, % CPUE. Mesh size of the net is shown at the top, along with the months and years that sampling took place. Sample sizes are reported as hours fished for the fyke and gill net data, and as number of stations across all years for the other data. Catch composition is % CPUE by number averaged over all surveys for that net type/habitat. Cells are coded such that darkest cells represent species/families with the greatest% CPUE for that net type/habitat. Richness (S), Simpson’s Index (D) and Shannon Index (H) for each habitat are shown at the bottom.
a
b
a Number of hours the net was fished standardized to a common net length (60 feet). b Most of the sculpin in the shelf midwater trawl catch were unidentified.
Three species that are commercially important outside the work (Chiperzak et al., 1995). Greenland Halibut reported here Arctic, Walleye Pollock (Gadus chalcogrammus), Pacific Cod (Gadus were 130–400 mm (Table 5), age 1–6 (Matta and Kimura, 2012) macrocephalus) and Greenland Halibut (Reinhardtius hippoglos- younger and smaller than those that recruit to the fishery in the soides), were only present in shelf demersal habitat (Table 4). Bering Sea (Barbeaux et al., 2013). None of these three species were Walleye Pollock ranged in size 80–320 mm (Table 5). These fish present in the shelf ichthyoplankton (Table 6), indicating that they were 1–3 years old, and smaller at age than Bering Sea Pollock are likely not yet spawning at Arctic latitudes, but were trans- (Rand and Logerwell, 2010) and thus not likely to be large enough ported from the Bering Sea after being spawned there. to be of commercial value. Pacific Cod were 240–330 mm (Table 5), The lagoon habitat appears to play a role in the life history of likely age 1–3 (Matta and Kimura, 2012). Greenland Halibut spec- salmonids, forage fishes, and Saffron Cod. Furthermore, there were imens have been found across the Beaufort Sea previous to this two species that appeared to use the lagoon habitat to an extent 124 E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132
Table 5 Fish length in mm (mean and range) in the Beaufort Sea. Mesh size of the net is shown at the top, along with the months and years that sampling took place and the number of fish measured (all species combined). ‘‘ND’’ stands for ‘‘no data’’. The cells are coded the same as Table 1, and thus indicate relative % CPUE.
a
a
a
a Sample size = 1.
Table 6 Presence/absence of taxa in the ichthyoplankton, in the Beaufort Sea August 2008 (n = 28 stations).
Family Common name Scientific name Eggs Larvae Juveniles AMMODYTIDEA Pacific Sand Lance Ammodytes hexapterus X GADIDAE Unidentified cod X Arctic Cod Boreogadus saida XX X Saffron Cod Eleginus gracilis XX COTTIDAE Arctic Staghorn Sculpin Gymnocanthus tricuspis X Shorthorn Sculpin Myoxocephalus scorpius X STICHAEIDAE Unidentified pricklebacks X Slender Eelblenny Lumpenus fabricii X Daubed Shanny Leptoclinus maculatus X LIPARIDAE Kelp Snailfish Liparis tunicatus X Unidentified snailfish X PLEURONECTIDAE Unidentified flounder X Longhead Dab Limanda proboscidea X Bering Flounder Hippoglossoides robustus XX
not usual for their taxa, a sculpin and a flatfish (Table 4). Fourhorn benthic habitats. In contrast, the other sculpin species were found Sculpin (Myoxocephalus quadricornis) was one of the dominant spe- only outside the lagoon from the beach to the shelf. Arctic Flounder cies in the lagoon and was not present in shelf midwater and (Pleuronectes glacialis) were only caught in the lagoon. Other E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 125
Table 7 Norcross, 2011), were present in these habitats closer to shore 2 Mean density (No./10 m ) of most abundant taxa in the ichthyoplankton, in the (Table 5). However, age-0 fish were also present further offshore Beaufort Sea August 2008 (n = 28 stations). Most of the catch was larval fish, with a along with older fish. For example, Arctic Cod up to age 3+ were few juvenile Arctic and Saffron Cod. caught in the shelf midwater and shelf benthic habitats along with 2 Common name Scientifica name Mean density (No./10 m ) age-0 fish. Thus the beach and nearshore habitats do not appear to Arctic Cod Boreogadus saida 4.7 be the only habitats used as nursery areas; although older fish may Saffron Cod Eleginus gracilis 0.7 prefer offshore habitats. Bering Flounder Hippoglossoides robustus 0.3 Longhead Dab Limanda proboscidea 0.4 3.2. Chukchi Sea
Salmonids (Salmonidae) were found almost exclusively in the flatfishes were only present outside the lagoon from the nearshore surface waters of the shelf, with the exception of a relatively low to shelf. Another indication that the lagoon habitat may be unique catch of Arctic Cisco (Coregonus autumnalis) and Pink Salmon in is that taxonomic diversity (D and H) in the fyke net catch was the the beach habitat (Table 8). This is not surprising, given that the highest of the habitats examined (Table 4). Perhaps some fish taxa surface trawl survey was designed to assess the distribution of prefer the shallow, warmer and brackish waters of lagoon habitats juvenile salmonids. Pink and Chum Salmon were the dominant compared to other habitats offshore (Craig et al., 1982). For exam- species in 2007 and Chum were in 2009. Chinook, Coho and ple, it has been noted that the abundances of most anadromous Sockeye Salmon were caught at relatively low % CPUE. As discussed species in nearshore and lagoon waters of the Beaufort Sea are cor- above for the Beaufort Sea results, it is unusual to catch Chinook related with warm temperatures and low salinities (Craig, 1984). Salmon in the Arctic (Stephenson, 2006; Irvine et al., 2009). There may also be a benefit from greater availability of Salmonids ranged from 170 to 331 mm (Table 9) and were thus terrestrial-based nutrients (Dunton et al., 2006) and abundant food age-0 (Chinook) to juveniles or maturing (Farley et al., 2009; resources, predominantly epibenthic mysids and amphipods (Craig Moss et al., 2009). The relatively high CPUE of juvenile Pink and and Haldorson, 1981; Griffiths and Dillinger, 1981; Craig, 1984). In Chum Salmon during 2007 (Table 8) provided some evidence that addition, anadromous fishes may use lagoons as migration corri- increased warming in the Arctic, evidenced by the 2007 sea ice dors during spring and fall migration (Craig, 1984). Alternatively, minimum (Woodgate et al., 2010), may be beneficial for future sal- there may be conditions in the lagoon that exclude other fishes, monid productivity in the region. For instance, adult Pink Salmon such as high seasonal variability in temperature and salinity. For were captured in anomalously high numbers within subsistence example, in North Salt Lagoon, surface salinity in late June is 0–4 nets off Barrow, Alaska during 2008 (E. Farley, unpubl.). Perhaps and rises to 27–29 over the course of the summer (T. Sformo, not surprisingly, Pink Salmon catch made up 22% of total CPUE in unpubl.) and lagoon temperatures can fluctuate between 0 and the lagoon gill net survey in the Beaufort Sea (this study). 14 °C(Craig et al., 1982). Juvenile Pink Salmon return to their natal spawning streams after Our data on fish distribution and size across habitats, combined one year in the ocean, suggesting that the high CPUE of juvenile with ichthyoplankton data generates ideas about the spawning and Pink Salmon during 2007 was linked to increased catches the fol- ontogenetic movements of several taxa. As discussed above, Arctic lowing year. Similarly, anomalously high numbers of adult Chum Cod appears to use all habitats for most life history functions, with Salmon were captured off Barrow in subsistence nets during the largest fish staying/moving offshore to the shelf benthic habi- 2009 and 2010 (E. Farley, unpubl.), following the typical 2–3 year tat. Whereas Saffron Cod appear to spawn on the shelf and move marine life history for these fish. The summer sea temperatures into nearshore and the lagoon as they age. Pricklebacks and eel- in the Chukchi Sea were very warm during 2007 (Woodgate blennies (Stichaeidae) were larger away from the beach (Table 5) et al., 2010), potentially contributing to the success of juvenile and were present as larvae over the shelf (Table 6), suggesting that Pink and Chum Salmon during that year. Thus future warming in spawning occurs on the shelf, larvae are transported inshore, and the Arctic, particularly during summer months, may contribute fish move offshore as they age. Snailfish (Liparidae) larvae were to better early marine growth for juvenile salmonids and increased present on the shelf (Table 6), suggesting they spawn there. In con- returns to spawning habitat (Andrews et al., 2009; Moss et al., trast, eelpouts (Zoarcidae) and poachers (Agonidae), were not 2009). found in the ichthyoplankton on the shelf (Table 6), suggesting Forage fishes (Smelts (Osmeridae), Pacific Herring and Pacific they spawn elsewhere or at an early season. Several species that Sand Lance) were found in all habitats, although Pacific Sand were dominant or restricted to the lagoon and/or beach habitats Lance was the only forage species caught in the beam trawl were not found in the shelf ichthyoplankton: Fourhorn Sculpin, (Table 8). The greatest relative densities of forage fishes were Arctic Flounder, sticklebacks (Gasterosteidae), and Capelin found in the beach and shelf surface habitats, in particular (Tables 4 and 6). We hypothesize that they spawn in the lagoon Capelin. Capelin were caught in a somewhat similar range of and beach habitats where the adult stages were found. In contrast, lengths in all habitats, although the smallest fish (29 mm) were Pacific Sand Lance, which was found only in the beach habitat as found in the beach habitat and the largest (180 mm) in the shelf adults (Table 4) was present in the shelf ichthyoplankton surface waters (Table 9). This range of lengths likely corresponds (Table 6). Pacific Sand Lance spawn in subtidal or intertidal sand to post flexion larvae (Doyle et al., 2002) to age 3+ (Brown, substrates (Robards et al., 1999) and our data suggest that the lar- 2002). The length of Rainbow Smelt (Osmerus dentex) increased vae (and perhaps the eggs) are then transported offshore. Seasonal from the nearshore to the shelf from a minimum size of 72 mm surveys of multiple life stages of fish in all habitats would address to a maximum of 300 mm (Table 9). Pacific Herring were caught the hypotheses and unknowns about the life history of these taxa in a similar range of lengths in the shelf surface and benthic habi- discussed here. tats. The largest range of Herring sizes occurred in the shelf surface Smaller, presumably younger, fish were found in the beach and habitat (in 2012), 78–313 mm (Table 9), likely ages <1 to 9+ nearshore benthic habitats, consistent with the hypothesis that (Lassuy, 1989). Capelin and Pacific Sand Lance spawn on or near these are nursery areas. For example age-0 Arctic Cod (Gallaway the beach (Brown, 2002; Robards et al., 1999), thus the catches and Norcross, 2011), Saffron Cod (Norcross et al., 2015), Slender of larval and age-0 forage fishes suggests that after spawning, juve- Eelblenny (Lumpenus fabricii; Norcross et al., 2015), Capelin nile fishes spend some amount of time in the nearshore before (Doyle et al., 2002), and sculpin (Cottidae; Gallaway and moving offshore into deeper waters. Large spawning events of 126 E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132
Table 8 Catch composition (% CPUE) from each net type/habitat in the Chukchi Sea. Mesh size of the net and survey months are shown at the top. Sample size is the number of stations sampled summed over all years. Cells are coded such that darkest cells represent species/families with the greatest% CPUE for that net type/habitat. Richness (S), Simpson’s Index (D) and Shannon Index (H) for each habitat are shown at the bottom.
Capelin on beaches near Barrow have been reported (S. Johnson, Arctic Cod larvae were one of the top four most abundant taxa in unpubl.), whereas spawning areas of Pacific Sand Lance and other the ichthyoplankton catch (Table 11), suggesting that they use forage fishes in the Arctic are largely unknown. the shelf habitat for larval development and possibly spawning. Arctic Cod were present in all habitats. They made up relatively The pattern in fish lengths and ichthyoplankton catch suggests that large portions of the catch in the nearshore and shelf benthic habi- Arctic Cod use nearshore and shelf habitats for multiple life history tats (Table 8). The minimum size of Arctic Cod was somewhat sim- functions, with the older Cod staying/moving offshore to the shelf ilar across habitats, 30–40 mm (Table 9), age-0 (Gallaway and benthic habitat. Norcross, 2011). However, the maximum length of Arctic Cod Saffron Cod were likewise found in all habitats, making up a increased from the beach to the benthic shelf from 66 mm to large portion of the catch in the shelf surface habitat (Table 8). 260 mm (age-0/1 to age-3+ (Gallaway and Norcross, 2011)). Saffron Cod had a similar size distribution as Arctic Cod across E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 127
Table 9 Fish length in mm (mean and range) in the Chukchi Sea. Mesh size of the net is shown at the top, along with the months and years that sampling took place and the number of fish measured (all species combined). ‘‘ND’’ stands for ‘‘no data’’. The cells are coded the same as Table 8, and thus indicate relative % CPUE.
a
a If no min–max shown, only one fish was measured.
habitats. The smallest fish were 26–40 mm (Table 9), age-0 Documentation of mature adult Walleye Pollock in the Chukchi is (Norcross et al., 2015). The maximum lengths increased from needed to confirm spawning activity for this species in the 50 mm in the beach habitat to 360 mm on the shelf, likely span- Arctic. In addition, determining the developmental stage of eggs ning at least 3 age classes (Table 9). This suggests that their use caught in the Arctic could help reveal whether eggs may have been of different habitats through development is similar to that of transported from the south or were spawned locally. Pacific Cod, Arctic Cod. another important commercial cod in the Bering Sea, ranged in size Pacific Cod and Walleye Pollock, important commercial cod from 100 to 254 mm (Table 9), likely age 1–2 (Matta and Kimura, (Gadidae) species in the Bering Sea, were found in the nearshore 2012). Pacific Cod larvae were not found in the ichthyoplankton and shelf benthic habitats, at low relative CPUE (0.5% or less; (Table 10) so we hypothesize that these fish were spawned in Table 8). Walleye Pollock were also found in the shelf surface habi- the Bering Sea and transported north. tat at low % CPUE (Table 8). Walleye Pollock ranged in size from 58 Flatfishes (Pleuronectidae) were found in all habitats. The great- to 160 mm (Table 9). These fish were likely mostly age-1 to age-2 est number of flatfish species and the greatest relative CPUE (Brown et al., 2001; Hinckley, 1984) and thus were not commer- occurred in the shelf benthic habitat (Table 8). Bering Flounder cially valuable (Walleye Pollock recruit to the Bering Sea fishery (Hippoglossoides robustus) and Yellowfin Sole (Limanda aspera) at age-3 or-4 (Ianelli et al., 2013)). Although no adult Walleye dominated the shelf benthic flatfish catch, although the % CPUE Pollock were caught, their eggs, larvae and juveniles were found was not very large (around 5%). Species that are commercially in the shelf ichthyoplankton survey (Table 10). These could have important in the Bering Sea, Yellowfin Sole, Greenland Halibut been transported into the Chukchi Sea from the Bering Sea, or and Alaska Plaice (Pleuronectes quadrituberculatus), ranged in aver- could have been spawned and reared in the north. age size from 45 to 191 mm (Table 9). This corresponds to ages 0–2 128 E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132
Table 10 Presence/absence of taxa in the ichthyoplankton, in the Chukchi Sea September 2007–2011 (n = 218 stations, all years).
Family Common name Scientific name 2007, 2010, 2011 2009 Eggs Larvae Juveniles Eggs Larvae OSMERIDAE Capelin Mallotus villosus XX Unidentified smelts X AMMODYTIDAE Pacific Sand Lance Ammodytes hexapterus X GADIDAE Arctic Cod Boreogadus saida XX X X Walleye Pollock Gadus chalcogrammus XX X X Unidentified cod X COTTIDAE Butterfly Sculpin Hemilepidotus papilio XX Arctic Staghorn Sculpin Gymnocanthus tricuspis X Spatulate Sculpin Icelus spatula XX X Shorthorn Sculpin Myoxocephalus scorpius X Hamecon Artediellus scaber X Unidentified Myoxocephalus X STICHAEIDAE Slender Eelblenny Lumpenus fabricii XX Daubed Shanny Leptoclinus maculatus XX Blackline Prickleback Acantholumpenus mackayi X Fourline Snakeblenny Eumesogrammus praecisus X Stout Eelblenny Anisarchus medius X Arctic Shanny Stichaeus punctatus X Unidentified Lumpenus X LIPARIDAE Unidentified Liparis X Variegated Snailfish Liparis gibbus X Kelp Snailfish Liparis tunicatus XX AGONIDAE Arctic Alligatorfish Aspidophoroides olrikii XX Gray Starsnout Bathyagonus alascanus X Alligatorfish Aspidophoroides monopterygius X PLEURONECTIDAE Bering Flounder Hippoglossoides robustus XX Unidentified Limanda XX Yellowfin Sole Limanda aspera X Longhead Dab Limanda proboscidea X Sakhalin Sole Limanda sakhalinensis X Alaska Plaice Pleuronectes quadrituberculatus XX HEXAGRAMMIDAE Whitespotted Greenling Hexagrammos stelleri XX Masked Greenling Hexagrammos octogrammus X
trawls were sub-adults. Age data and collection of spawning Table 11 females would clarify whether, when and where these species Mean density (No./10 m2) of most abundant taxa in the ichthyoplankton, in the Chukchi Sea September 2007–2011 (n = 218 stations, all years). are spawning in the Chukchi Sea. We examined the shelf surface trawl data for each year (2007 2 Common name Scientific name Mean density (No./10 m ) and 2012) separately because of striking between-year differences 2007, 2010, 2011 2009 in catch composition. In 2007 Saffron Cod dominated the catch Arctic Cod Boreogadus saida 0.02 1.3 whereas in 2012 Capelin were dominant (Table 8). 2007 was an Bering Flounder Hippoglossoides robustus 2.5 anomalous year due to warm water advected to the Chukchi Yellowfin Sole Limanda aspera 80.2 0.2 (Woodgate et al., 2010), coincident with the first new record ice Longhead Dab Limanda proboscidea 0.8 minima (NCAR, 2007). Cooler summer water temperatures pre- vailed in the Chukchi Sea during years after 2007 (Proshutinsky et al., 2011; Timmermans et al., 2012). Capelin are thought to pre- for Greenland Halibut and ages 0–6 for Yellowfin Sole (Matta and fer cooler water temperatures (Anderson and Piatt, 1999), so this Kimura, 2012), younger and smaller than those that recruit to difference between 2007 and 2012 ocean conditions may explain the fishery in the Bering Sea (Barbeaux et al., 2013; Wilderbuer the difference in species composition in the surface waters. et al., 2013). Alaska Plaice was not found in the shelf ichthyoplank- We examined data from two different gear types deployed in ton (Table 10), suggesting they are not spawning in the Arctic. the same habitat, the benthic shelf, and not surprisingly the catch Greenland Halibut were similarly not found in the ichthyoplankton composition was different. The shelf plumb staff beam trawl catch (Table 10), but Greenland Halibut larvae grow to large sizes in the was dominated by sculpins (Arctic Staghorn (Gymnocanthus tricus- plankton (80 mm in the Bering Sea, Duffy-Anderson, unpubl.) and pis) and Shorthorn (Myoxocephalus scorpius)) and by Slender may be too large to be sampled effectively by the zooplankton nets Eelblenny. In contrast, the catch of the larger mesh shelf 83-112 used in these surveys. In fact, Greenland Halibut ranging in size Eastern otter bottom trawl was dominated by Arctic Cod from 63 to 80 mm were caught in the shelf surface trawl (Table 8). Arctic Cod were present in the beam trawl catch, but (Table 9) so it appears that this species may spawn in the Arctic. at lower relative density. Similarly, Saffron Cod were caught in Yellowfin Sole was one of the top four species in the ichthyoplank- both nets, but at a lower relative density in the beam trawl. ton, dominating the catch by two orders of magnitude in some sur- Differences in net size and speed of deployment likely contributed veys (Table 11). Although Greenland Halibut and Yellowfin Sole to this pattern. A paired trawl experiment in the Chukchi Sea dur- larvae were found in the Chukchi, the fish caught in the bottom ing the 2012 Arctic EIS survey allowed for a comparison of the E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 129 catch of the beam trawl and the 83-112 trawl data (Britt et al., their marine phase. Surveys of the surface waters of the Beaufort 2013). Although the two trawls caught a similar number of fish and the lagoons of the Chukchi are needed to resolve this apparent taxa per haul, a station-by-station comparison showed that the difference in habitat use of salmon. Pink and Chum Salmon were catch composition was very different: 33% of the fish species common salmon species in both Seas, not surprisingly, given that caught were gear-specific. The beam trawl was more effective at they are Arctic residents. Chinook Salmon were also caught, albeit catching juvenile fishes, whereas the 83-112 trawl was more effi- at relatively low abundance, in both Seas. Chinook Salmon are cient at capturing larger and more mobile organisms. Britt et al. rarely seen in the Arctic leading to speculation that their range (2013) conclude that the two trawls are complementary sampling may be expanding due to climate change (Moss et al., 2009), but tools and used together provide a more inclusive catalog of species more evidence is needed to confirm this hypothesis (Stephenson, composition than either gear used alone. 2006). Our data on fish distribution and size across habitats in the Forage fishes (Pacific Sand Lance, Pacific Herring, Capelin, Chukchi Sea, combined with ichthyoplankton data generate Rainbow Smelt) in both Seas seem to prefer habitats relatively hypotheses regarding life history and habitat use of several taxa. close to shore such as the lagoon, beach and nearshore. As dis- As discussed above, it appears that Arctic and Saffron Cod use mul- cussed above (in the Beaufort Sea section), lagoon habitat may be tiple habitats for multiple life history functions, with the older fish preferred due to the relatively warm and low salinity waters, abun- staying/moving offshore. A similar pattern was observed for other dant food resources and proximity to natal streams for anadro- taxa. Sculpins (Cottidae) were present in all habitats, with greatest mous fishes. The brackish water characteristic of lagoons can % CPUE in the shelf surface and benthic habitats (Table 8). The lar- extend out to the beach and nearshore depths (<10 m), is distinct gest fish were in the shelf benthic, likely age-4 or higher (Table 9). from adjacent marine waters and provides important feeding habi- Although fish were smaller and likely younger towards shore tat for anadromous and marine fishes in summer (Craig, 1984). (age-0 to age-3), smaller, presumably age-0 sculpins were found During winter this estuarine band is absent and most anadromous offshore with the larger sculpins (Gallaway and Norcross, 2011). fishes return to North Slope rivers and marine fishes move offshore Pricklebacks (Stichaeidae) were likewise present in all habitats, as nearshore waters freeze. The nearshore of the Chukchi Sea coast with greatest relative CPUE in the nearshore benthic and shelf ben- is similarly warm and low salinity during summer due to solar thic habitats (Table 8). Fish increased in size from the beach out to heating and freshwater inputs (R. Heinz, unpubl.). Capelin and the offshore shelf habitat being as large as 205 mm in the shelf sur- Pacific Sand Lance use beach and intertidal habitats for spawning face habitat and as large as 390 mm in the shelf benthic habitat in summer (Robards et al., 1999). Mass spawning of Capelin has (Table 9), likely greater than age-3 (Gallaway and Norcross, been observed on beaches near Barrow in previous studies 2011). Similar to the cods (Gadidae) and sculpins, age-0 prickle- (George et al., 2009). Forage fishes also occurred in the surface backs (30–50 mm) were also caught in the shelf benthic habitat waters of the Chukchi Sea shelf with some species, such as along with the older, larger fish (Table 9). Snailfishes (Liparidae) Capelin, dominating the catch. A surface trawl survey in the and poachers (Agonidae) were found in all habitats but at relatively Beaufort Sea is needed to determine whether this distribution is low% CPUE (2% or less; Table 8). Eelpouts (Zoarcidae) were found in unique to the Chukchi Sea or typical of Arctic forage fishes. all habitats, except the beach, at 4% CPUE or less (Table 8). Arctic Cod dominated the benthic habitats of the nearshore and Snailfishes, eelpouts and poachers all increased in size from the shelf in both Seas. Arctic Cod were also relatively abundant in the beach through the nearshore and to the offshore surface and bot- shelf midwater of the Beaufort Sea. Although we present no survey tom habitats (Table 9). Similar to the species discussed above, data from the Chukchi midwater habitat, preliminary results from smaller and presumably younger fishes were also present in the the 2012 and 2013 acoustic-trawl surveys of the Arctic Ecosystem offshore habitats along with the bigger, older fishes. Integrate Survey (EIS) show that the one of the primary acoustic Smaller, presumably younger, fishes were found in the beach targets observed in the midwater of the Chukchi Sea were age-0 and nearshore benthic habitats, suggesting these are nursery areas. Arctic Cod (https://web.sfos.uaf.edu/wordpress/arcticeis/). For example age-0 Arctic Cod (Gallaway and Norcross, 2011), We hypothesize that the life history distribution of Arctic Cod is Saffron Cod (Gallaway and Norcross, 2011), Slender Eelblenny similar for the Beaufort and Chukchi Seas: spawning and larval (Gallaway and Norcross, 2011), Capelin (Doyle et al., 2002) and development takes place on the shelf, development of age-0 fish sculpins (Gallaway and Norcross, 2011) were present in these habi- occurs throughout the nearshore and shelf and fish move/stay off- tats closer to shore. However, age-0 fishes were also present fur- shore as they age. The life history distribution of Arctic Cod in the ther offshore along with older fishes, age 3 and higher. Chukchi and Beaufort Seas has not been documented in detail. It is known that they spawn under sea ice during winter, between 3.3. Overall patterns November and March (Rass, 1968; Craig et al., 1982). The eggs are buoyant and remain at the surface through hatching (Graham The sampling effort differed among the two seas, particularly on and Hop, 1995). Larvae remain at the surface for several months the shelf, with fewer surveys occurring during fewer years in the after hatching, until September when they settle to the bottom Beaufort Sea compared to the Chukchi Sea. This could lead to bias (Baranenkova et al., 1966; Sekerak, 1982). Age-0 fish are known in fish community composition or distribution due to different to be planktonic and found in bays, fjords and offshore. Juveniles sample sizes and/or different oceanographic conditions among and adults are understood to be found either dispersed throughout years. Nonetheless, there were numerous similarities between the water column of concentrated in schools at the ice edge, along the patterns observed in the two seas. shorelines in summer and in deep offshore waters (Bradstreet Salmon (Oncorhynchus sp.) were most prevalent in the lagoon et al., 1986). Our synthesis of Arctic Cod distribution based on habitat in the Beaufort Sea and the shelf surface habitat in the the limited large scale survey data available provides a more cur- Chukchi Sea. However, no shelf surface surveys have been con- rent and more detailed state of understanding of how Arctic Cod ducted in the Beaufort, so it is as yet unknown if salmon use the may use different habitats throughout their life history. Field stud- surface waters as they do in the Chukchi. Conversely, no surveys ies focusing on Arctic Cod life history that would sample multiple of Chukchi lagoons have been conducted, so it is unknown if sal- age classes in multiple habitats throughout the year are needed to mon use lagoons as they do in the Beaufort. Lagoon habitat is less confirm and refine our ideas. prevalent in the Chukchi than the Beaufort, so it is possible that the We suggest that the distribution and habitat use of Saffron Cod salmon found in the Chukchi Sea are restricted to the shelf during was different between the two Seas. In the Beaufort, the data are 130 E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 consistent with fish spawning on the shelf and moving into the development include cod, forage fishes and salmonids. For many nearshore and lagoon as they age. In the Chukchi it appears that, taxa in our datasets age-0 fishes were found nearshore and older similar to Arctic Cod, they use nearshore and shelf habitats for fishes were further offshore consistent with the idea that the near- multiple life history functions with older fish staying or moving shore provides nursery habitat. However, this does not appear to offshore. As discussed above, no surveys have been conducted in be a straightforward ontogenetic offshore migration because at Chukchi lagoons, so the use of lagoons by Saffron Cod in this area least some age-0 fishes were present offshore with the older fishes. cannot be ruled out. However, given the relative paucity of lagoon Again, field studies of multiple ages classes in multiple habitats habitat in the Chukchi, it is possible that this habitat use behavior throughout the year would help resolve and interpret these pat- is unique to the Beaufort Sea. The little published information on terns. Arctic nursery habitat may not be typical, compared to other Saffron Cod life history indicates that they spawn in winter, temperate and tropical areas (Beck et al., 2001). In temperate and December–February, in relatively cold and shallow waters close tropical areas, nursery habitat often includes physical structure to shore. The eggs are demersal and non-adhesive. Larvae and juve- such as eel grass beds or kelp patches. Much of the nearshore areas niles have been caught in surveys of Norton Sound, Bering Strait of the Arctic are overlaid with shorefast ice for most of the year. Ice and eastern Bering Sea (Dunn and Matarese, 1987); and recently keels, extending as deep as 20–30 m, can cause significant bottom as an ‘‘invader’’ of nearshore habitats of Prince William Sound, scouring as the ice deforms in mid-winter and moves out in sum- Alaska (Johnson et al., 2009). As suggested above, for Arctic Cod, mer. Consequently, there are few physical features or vegetation to our synthesis provides the most current and detailed conceptual provide juvenile fish with cover in the nearshore. Instead of phys- models for the life history distribution of Saffron Cod and further ical cover, oceanographic conditions (i.e. temperature and salinity) surveys of multiple life history stages of Saffron Cod across seasons in nearshore waters during the Arctic summer may provide age-0 are needed. fish with a predator refuge that simultaneously traps prey and Species of cod and flatfish that are commercially important offers temperatures that optimize growing conditions (Jarvela elsewhere were found in both Seas: Walleye Pollock, Pacific Cod, and Thorsteinson, 1999). and Greenland Halibut. Yellowfin Sole were also found in the The relative abundance estimates of small fishes near shore Chukchi Sea. None of these species were found in the ichthy- could have been influenced by differences in gear type. The nets oplankton in the Beaufort Sea suggesting they are not yet spawning fished on the beach and in the nearshore benthic habitat had smal- that far north. In contrast, Walleye Pollock and Greenland Halibut ler mesh than the shelf surface trawl and shelf bottom trawl. The larvae were present in the Chukchi Sea, as were high abundances of beach and nearshore nets were also smaller in overall dimensions. Yellowfin Sole larvae. Larvae were present; however, adult fish of There is a possibility that bigger fish were able to avoid the smaller these species were not. Continued monitoring of multiple life mesh inshore nets, because they were towed at slower speeds than stages of Walleye Pollock and flatfishes in the Arctic, including the larger shelf bottom trawl. Another concern might be that the spawning adults, if present, will determine whether the ranges of larger mesh offshore nets were not capable of catching small fish. these valuable species are shifting north with climate change. However small fishes of many taxa were caught in the nets fished However, the current perspective is that bottom water tempera- offshore, so this bias does not appear to be a problem at the reso- tures in the Arctic are too cold to support spawning Walleye lution of the analyses discussed above. Pollock and that the sub-adult fish that are caught at high latitudes All the surveys that contributed to the synthesis of fish distribu- were advected by currents from spawning locations in the Bering tion and habitat use across habitats were conducted in spring-fall, Sea (Hollowed et al., 2013). In contrast, Greenland Halibut are ice-free seasons. This highlights the need for surveys of fishes in found in Arctic latitudes in the Atlantic and it is thought that there their overwinter habitats, which would need to be conducted is potential for the spawning range of Greenland Halibut to extend under the ice and in polynyas such as those near Wrangell and into the Pacific Arctic given appropriate temperature and feeding St. Lawrence Islands. conditions (Hollowed et al., 2013). Similarly, there is a potential for the range of Yellowfin Sole to extend into the Arctic given its 4. Summary presence at high latitudes and eclectic diet (Hollowed et al., 2013). Regardless of whether any of these species are spawning In summary, our synthesis of fish survey data across a spectrum in the Arctic at this time, none of the fish caught in our surveys of habitats in the Beaufort and Chukchi Seas revealed more similar- were large enough to be commercially valuable. ities than differences. Some highlights are that Chinook Salmon Patterns in taxonomic diversity across habitats differed between may be moving into the Arctic; and that the nearshore is a habitat the Beaufort and Chukchi Seas. The dominance of Capelin in the for forage fish across age classes and also a nursery area for other beach and shelf surface habitats of the Chukchi Sea resulted in the species. In addition, we document the presence of commercially lowest taxonomic diversity (D and H indices) compared to other important Walleye Pollock and flatfishes and although they are Chukchi habitats. This is in contrast to the Beaufort Sea where the not likely spawning in the Arctic now, the flatfishes have potential nearshore benthic, shelf midwater and shelf benthic habitats had to expand their range into the Arctic. Finally, we provide the most low diversity scores due to the dominance of Arctic Cod. The current and detailed conceptual models for the life history distri- Chukchi Sea shelf beam trawl catch data had the highest indices of bution of key gadids in Arctic food webs: Arctic and Saffron Cod. taxonomic diversity, due to the distribution of catch among gadid, We also identify research gaps, such as the need for surveys of sculpins, pricklebacks, eelpouts, and flatfish. No one species made the surface waters of the Beaufort Sea, surveys of the lagoons of up more the 30% of the total CPUE in the shelf beam trawl catch. the Chukchi Sea, and winter season surveys in all areas. We recom- The highest taxonomic diversity in the Beaufort Sea was observed mend field studies on fish life history that sample multiple age in the lagoon, due to the distribution of catch among salmonids, classes in multiple habitats throughout the year to confirm, resolve smelts, sticklebacks, cod, sculpins and flatfishes. and interpret the patterns in fish habitat use that we observed. Nearshore habitats have been shown to be nursery areas in Northeast Pacific marine systems, such as Southeast Alaska (Johnson et al., 2005), Bering Sea-Aleutian Islands (Thedinga Acknowledgements et al., 2008), Prince William Sound, Alaska (Norcross et al., 2001) and the Gulf of Alaska (Norcross et al., 1995; Brown, 2002). The authors thank 3 anonymous reviewers for their construc- Species groups using the nearshore in these systems for juvenile tive comments. This study is part of the Synthesis of Arctic E. Logerwell et al. / Progress in Oceanography 136 (2015) 115–132 131
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