Chapter 4. Synthesis of Arctic Alaska Marine Fish Ecology By Lyman K. Thorsteinson1 and Milton S. Love2 Abstract interpretive component (historical and ecological elements of biogeography) provides a meaningful approach for The compilation of data and information, its review, explaining the observed diversity relationships, synthesizing and the synthesis processes leading to the development of the information presented, and expressing our impressions individual species accounts focused on descriptive elements about outstanding needs. Historical biogeography addresses of Arctic Alaska’s marine fish fauna. The species accounts the origins of distributional patterns as determined from reflect the compilation and review of a large body scientific systematic studies. The paleoceanographic record is not information about the marine fishes off Alaska in United well-developed from this part of the Arctic and here States waters in the northern Bering Sea, north of the Bering we explore species origins in light of possible dispersal Strait, and throughout the circumpolar Arctic. The purpose and vicariance events as suggested by paleontology and of this synthesis is to interpret the whole of this biological geologic records, climatic histories, and known phylogenetic and ecological information in the context of the marine relationships. Ecological biogeography addresses the biogeography of the Chukchi and Beaufort Seas. This environmental relationships including physiochemical factors interpretive approach provides historical and contemporary (for example, temperature, salinity, dissolved oxygen, and perspectives to our descriptions of (1) patterns of species turbidity), mechanisms (for example, currents, migrations, occurrence, habitat and population relationships, and and movements), and biological processes (for example, (2) functional ecosystem processes that affect the distribution competition, predation, colonization, and reproduction) that and abundance of marine fishes, and, with respect to the limit the distribution, relative abundance, and productivity of present, (3) conceptual understanding and information needed a species. Information about body size and trophic position for resource management and conservation. The objectives also are reviewed because they are important parameters that of this synthesis focus on environmental relationships correlate with metabolic processes and other life history traits including physio-chemical factors (for example, temperature, (Romanuk and others, 2011). salinity, dissolved oxygen, and turbidity), mechanisms The descriptive component of biogeography is addressed (for example, currents, migrations, and movements), and in project tasks leading to an updated checklist of marine biological processes (for example, competition, predation, fishes, presentation of information in the species accounts, colonization, and reproduction) that collectively have limited and special analyses related to (1) new species occurrences the distribution, abundance, and productivity of marine fish and range extensions, (2) large-scale patterns of abundance populations through adaptations to Arctic conditions. from past and ongoing studies, and (3) identification of species likely to occur, but yet-to-be confirmed from the Chukchi and Beaufort Seas. The visualization of species information in new maps and depth profiles provides another dimension Introduction—A Biogeographic to evaluation of the status of baseline information than was previously available. This is especially relevant as it applies to Emphasis availability of age- or stage-specific information and related habitat relationships. Quantitative relationships between Individual species accounts present a large amount of age-and-length and size-at-length have been described for information about the biology, geography, and environmental several dominant species, but this information is dated. For factors affecting large-scale patterns of distribution and almost all species, information about stock structure and abundance. Collectively, this compilation of environmental population dynamics (that is, differential mortalities between information is foundational for an improved understanding life stages or age classes) remains to be described. Although of the descriptive and interpretive components of this many science gaps exist, compiling and integrating descriptive region’s biogeography (Nelson, 2006). Our focus on the and interpretive information-types allows a more detailed examination of linkages between geographic distributions, 1U.S. Geological Survey. evolutionary processes (patterns of life history variations), ecological factors, genetic diversity, and population dynamics 2University of California, Santa Barbara. 618 Alaska Arctic Marine Fish Ecology Catalog for the fauna as an initial approach to estimating effects of The estimates of marine fish diversity (occurrence) in environmental change (Winemiller, 2004; Benton and others, table 4.1, was from published literature or acquired through 2006). This approach illustrates why the information presented reliable sources of written communications, and represent in the species accounts is relevant to decision making and, for “working” totals from a field of ichthyology that is rapidly potential indicators species, a rationale for research priorities. changing. These changes relate to new discoveries, increased sampling, and new genetic tools for identification and better understanding of evolutionary relationships. The presence of 15 new marine fishes from the U.S. Arctic not reported Historical Biogeography in the Fishes of Alaska (Mecklenburg and others, 2002) has been confirmed for this report (table 2.2). Many of the The Chukchi and Beaufort Seas occupy a relatively small authors cited reported significant problems associated with region within the zoogeographic realm (Mecklenburg and species identifications (related these to unresolved taxonomic others, 2011) that has been used by classical ichthyologists issues), deficiencies in geographic sampling coverage, to describe the taxonomy and composition of the Arctic or access to existing data and information. Despite these marine fishes (Briggs, 1974; Andriashev and Chernova 1994; issues, the systematic comparisons help to begin to explain Eastman, 1997; and Mecklenburg and others, 2011). In Alaska, large-scale patterns of biodiversity including origins of the Arctic Realm includes the northern Bering Sea and marine 3 species distributions. environments beyond the EEZ . As such, it does not directly Biogeographic research has shown that fish species in correspond to conventional natural resource management areas the Pacific and Atlantic Oceans have similar zoogeographic in the Alaskan Arctic. The southern boundary of the province patterns with respect to latitudinal gradients, but not diversity in the Bering Sea is ecologically significant because the (Christiansen and others, 2008; Christiansen and others, area demarks a sharp gradient in diversity and abundance of 2013). In each ocean, species richness peaks in the tropics Arctic and Boreal marine fishes that is defined by temperature with sharp gradients between tropical and temperate waters. (<2 °C). As such, a natural rather than administrative faunal There is leveling off in decline of richness toward the poles separation is represented. For example, NOAA collected 86 (Roy and others, 1998). Using marine gastropod diversity species of marine fishes in the northern Bering Sea in 1981 data, Roy and others (1998) examined latitudinal gradients (Thorsteinson and others, 1984) compared to the 300 species in the Atlantic Ocean with respect to ecological traits (that reported from the southeastern Bering Sea (Wilimovsky, is, range size, habitable area, and input of solar energy). The 1974). The zonation is important to contemporary Arctic greatest correlation reported was between diversity and sea issues with respect to extralimital species and northerly surface temperature (a proxy for solar input) suggesting that, shifts in distributions and range expansions associated with if the relation was causal, it probably was linked through some climate change and potential fisheries. The importance of the aspect of production. Because the physical mechanisms of Bering Strait with respect to geologic and climatic history dispersal for marine invertebrates and fishes are similar (or and origins and exchanges of fishes, especially during the late the same), process effects—such as production cycles and Pleistocene, has been shown to be critical to understanding events—would similarly influence geographic distribution and Pacific influences on Arctic fauna (for example, Mecklenburg abundance patterns. and others, 2011). In areas where regional faunas are relatively well known, A systematic comparison of the marine fishes reported Briggs and Bowen (2012) described a high concordance from the Arctic province, marginal seas of the Arctic Ocean, between levels of endemism in fishes, molluscs, and other and Bering Sea provides clues and insights about the biota. However, Roy and others (1998) could not explain evolutionary processes (origins, rates of endemism) underlying latitudinal gradients in the North Atlantic based on recent current patterns of taxonomic representation (zoogeographic geologic history. By contrast, Vermeij (1991) and Briggs patterns, chapter 2). The comparison of marine fish faunas (1995, 2003) described the biogeographic consequences from adjacent waters also is instructive with respect