Growth and Condition of Arctic Cisco and Broad Whitefish as Indicators of Causeway-Induced Effects in the Prudhoe Bay Region, Alaska

Abstract

We describe trends in growth and condition of Arctic cisco Coregonus autumnalis and broad whitefish C. nasus in the Prudhoe Bay region of northern Alaska for the period 1985–1989 to evaluate sublethal effects of changes in hydrography induced by building a causeway into the Beaufort Sea. Growth (increase in length) of age‐1 and age‐2 fish of both species was positively correlated with temperature, which explained 77–92% of the sample variance, Condition (whole wet body weight at a given length) was less correlated with temperature than was growth. However, small broad whitefish, which do not venture far from river mouths, showed a positive association between condition and salinity. Conversely, large broad whitefish, which range away from the rivers, exhibited a negative association with salinity. The foraging range of large broad whitefish may be restricted by high‐salinity water masses that, however, may deliver higher‐than‐normal levels of prey to the habitats near river deltas used by small fish. Arctic ciscoes appeared able to exploit a wide range of temperature or salinity conditions equally well, as indicated by their relatively constant condition over the 5‐year period. Growth of age‐1 and age‐2 Arctic ciscoes and broad whitefish was estimated to have been reduced by an average of 4–6% by causeway‐related temperature changes over the 5‐year study period (range of annual values was 0–10%). This magnitude of change is not believed to be important to the ecology of the two species.

Intra- and Interseasonal Changes in the Relative Condition and Proximate Body Composition of Broad Whitefish from the Prudhoe Bay Region of Alaska

“…The Sagavanirktok River, which supports a spawning population of broad whitefish (Fechhelm et al 1992;Griffiths et al 1992), empties into the Beaufort Sea just east of Prudhoe Bay, Alaska ( Figure 1). The river delta is 16 km wide and is fronted by a shallow shoal (<2 m deep) that extends 3-4 km seaward.…”

“…Aging comparisons.-A distinct characteristic of the broad whitefish population is the discrete size segregation of younger age-classes ( Figure 2). The age of individual size-groups can be inferred and tracked intra-and interseasonally based upon the complete length-frequency time-series profile that has been compiled over the past 13 years of studies (Fechhelm et al 1992;Griffiths et al 1992). Length-frequency profiles ( Figure 2) were compiled for each of 12 dissection periods (i.e., early or late summer; 1988-1993).…”

“…The linear model was generated with data from all dissected fish collected over the 9-year sam-pling period exclusive of age-0 fish and fish that were judged to be sexually mature. Age-0 fish were not included because they do not emerge from the Sagavanirktok River until mid-August (Fechhelm et al 1992;Griffiths et al 1992) and there was concern that their weight-length relationship could be biased toward environmental conditions outside the study area. Sexually mature fish were not included because our study was directed toward seasonal changes in condition relative to feeding and overwintering strategy and not toward changes linked to gonadal development.…”

“…Anadromous and amphidromous fishes of the are needed to survive the long Arctic winter (Craig Alaskan Beaufort Sea have adapted life history 1984, 1989Fechhelm et al 1992;Griffiths et al strategies that reflect the physical cycles of their 1992). Arctic environment.…”

Estimating the Hydrographic Effects of Prudhoe Bay Causeway Breaches Using the Before-After Control-Impact (BACI) Analysis

“…Oceanography and fishery studies have been conducted in the Prudhoe Bay region of Alaska since the late 1970s to evaluate possible effects of oil and gas development in the Beaufort Sea (e.g., Craig and Haldorson, 1981;Mangarella et al, 1982;Gallaway et al, 1983Gallaway et al, , 1991Savoie andWilson, 1983, 1986;Moulton et al, 1986;Hachmeister et al, 1987Hachmeister et al, , 1991Fechhelm et al, 1989;Niedoroda and Colonell, 1990;Short et al, 1990;Robertson, 1991;Griffiths et al, 1992Griffiths et al, , 1998Morehead et al, 1992aMorehead et al, , b, 1993. A major issue has been the construction of solidfill, breached causeways along the coast and the effect they might have on the coastal habitats and feeding dispersals of diadromous fishes in the region (U.S. Army Corp of Engineers, 1980, 1984.…”