Geology topics

John F. Piatt

Publications and source records attributed to John F. Piatt.

At least 127 records · Page 7Linked to original sources

USGS2000

Monitoring seabird populations in areas of oil and gas development on the Alaskan Continental Shelf: A computerized pelagic seabird atlas for Alaska

Seabirds are the most visible and vulnerable victims of oil pollution in marine waters. As demonstrated by the "Exxon Valdez" spill (Piatt et al. 1990), we cannot predict when or where an accident leading to pollution might occur in Alaska, or where oil will eventually end up traveling from a point source of pollution. It is therefore prudent to document the abundance and distribution of seabirds throughout Alaska in order to: i) assist in the planning and development of future oil fields, ii) identify areas with significant and predictable aggregations of seabirds so that these areas might be avoided, if possible, in the extraction and shipment of oil, and, iii) mitigate and assess the impact of oil pollution if and when it occurs.

Report↗

USGS1999

The adrenocorical stress-response of Black-legged Kittiwake chicks in relation to dietary restrictions

In this study we examined hormonal responses of Black-legged Kittiwake ( Rissatridactyla ) chicks to experimental variations in energy content and nutritional quality (low or high lipid to protein ratio, LPR) of their food. Starting at the age of 10 days, chicks were fed either high or low LPR fish at 30, 50, 70 and 100% of ad libitum energy intake. After 20 days of treatment, chicks were exposed to a standardized acute handling and restraint stress protocol, where a baseline sample was taken immediately after taking a chick from the nest, and three additional blood samples were taken at intervals up to 50 min. Testosterone and corticosterone titres in plasma were measured via radioimmunoassay. We found that baseline testosterone levels were not significantly affected by the experimental treatments. Food-restricted chicks had elevated baseline and acute stress-induced levels of corticosterone compared to chicks fed ad libitum. An elevation of circulating levels of corticosterone in energetically stressed individuals was further magnified by low nutritional quality of food. Baseline and acute stress-induced corticosterone levels of chicks were negatively correlated with their fat reserves. We conclude that the physiological condition of Black-legged Kittiwake chicks can be assessed reliably by measuring circulating levels of corticosterone. We discuss short- and long-term effects of elevated corticosterone secretion in food-stressed nest-bound chicks.

Journal of Comparative Physiology B: Biochemical, ↗

USGS1999

Changes in proximate composition and somatic energy content for Pacific sand lance ( Ammodytes hexapterus ) from Kachemak Bay, Alaska relative to maturity and season

Mean dry-weight energy values of adult Pacific sand lance ( Ammodytes hexapterus ) peaked in spring and early summer (20.91 kJg −1 for males, 21.08 kJg −1 for females), then declined by about 25% during late summer and fall (15.91 kJg −1 for males, 15.74 kJg −1 for females). Late summer declines in energy density paralleled gonadal development. Gender differences in energy density (males<females) were only apparent from August to October. Adult sand lance spawn in October, entering the winter with close to their minimum whole body energy content. Juvenile sand lance exhibited a relatively constant protein to lipid ratio until they reached 80 mm fork length. Thereafter, relative proportions of protein remained constant while lipid proportions increased significantly. Dry weight energy densities of juveniles increased from a minimum 16.67 kJg −1 to a maximum of 19.68 kJg −1 , and (per g) are higher than adults in late summer. The seasonal food value of adult sand lance to predators varies markedly, but maximum energetic value coincides with important feeding periods for marine mammals, fish, and seabirds.

Alaska↗

USGS1999

Marine birds and mammals of the Pacific Subarctic Gyres

The importance of the subarctic gyres of the North Pacific Ocean to marine birds and mammals is poorly known because of a paucity of data spanning appropriate scales of time and space. The little information that is available indicates the western subarctic gyre (WSAG) is more productive than the eastern subarctic gyre (ESAG). In summer the WSAG supports a greater density and higher biomass of seabirds than the ESAG, including at least two species that are more abundant at nesting colonies in the eastern subarctic. Perhaps most revealing of the seabird distributions in this regard is that of southern hemisphere shearwaters (Puffinus spp.) that overwinter in the North Pacific. Their biomass is an order of magnitude greater than that of any northern hemisphere species and is three-fold greater in the WSAG than in the ESAG. Several species of cetaceans also appear to be, or to have been prior to commercial depletions, more abundant in the WSA. Among the many prey species consumed by marine birds and mammals, squids and fishes in the family Myctophidae predominate overall. Other forage species, notably euphausiids, Pacific saury (Cololabis saira) and Atka mackerel (Pleurogrammus monopterygius) are important at times to certain species. The principal exceptions to this generalization are baleen whales and small seabirds that consume zooplankton. Interannual and decadal-scale variability in the physical environment and food web production affect seabirds and marine mammals at sea and at coastal breeding locations around the margins of the gyres.

Progress in Oceanography↗

USGS1999

Maturation, fecundity, and intertidal spawning of Pacific sand lance in the northern Gulf of Alaska

Pacific sand lance Ammodytes hexapterus in Kachemak Bay, Alaska, showed no sexual dimorphism in length-to-weight (gonad-free) ratio or length-at-age relationship. Most matured in their second year, males earlier in the season than females, but females (31%) attained a higher gonadosomatic index than males (21%). Sand lance spawned intertidally once each year in late September and October on fine gravel or sandy beaches soon after the seasonal peak in water temperatures. Sand lance in Cook Inlet and Prince William Sound displayed similar maturation schedules. Schools were dominated 2: 1 by males as they approached the intertidal zone at a site where spawning has taken place for decades. Sand lance spawned vigorously in dense formations, leaving scoured pits in beach sediments. Fecundity of females (93–199 mm) was proportional to length, ranging from 1468 to 16 081 ova per female. About half of the overall spawning school fecundity was derived from age group 1 females (55% of the school by number). Spawned eggs were 1·02 mm in diameter, demersal, slightly adhesive, and deposited in the intertidal just below the waterline. Sand lance embryos developed over 67 days through periods of intertidal exposure and sub-freezing air temperatures.

Alaska↗

USGS1999

Time-budgets of Common Murres at a declining and increasing colony in Alaska

We observed Common Murres (Uria aalge) at two breeding sites in lower Cook Inlet, Alaska, to determine whether food availability was reflected in their time-budgets at each colony. Catches of forage fish in nets and relative biomass were greater around a murre colony that has been increasing for the past 25 years than around a colony that has been decreasing over the same time period. Murres spent much more time 'loafing' on their breeding ledges at the increasing colony, particularly during the incubation period and during evening hours. However, there was little or no difference between colonies in chick feeding rates, chick growth rates, or productivity. It appears that murres at the declining colony devote more time to foraging and have less discretionary time ashore. Because this had little apparent affect on their ability to feed and rear chicks, the population decline must be due to other factors. In any case, attendance time-budgets provide a more sensitive index of food availability than other breeding parameters at murre colonies.

Condor↗

USGS1999

Vocalizations of the Kittlitz's Murrelet

We present the first documentation of Kittlitz's Murrelet (Brachyramphus brevirostris) vocalizations, based on recordings made in Glacier Bay, Alaska, in 1994. We identified two apparently related types of calls: groan and quack. The Kittlitz's Murrelet calls were markedly different from the most common calls of the congeneric Marbled Murrelet (Brachyramphus marmoratus), but shared characteristics with the Marbled Murrelet's less common 'groan' call. Phylogeny, breeding biology, and habitat characteristics may explain relationships between the congeneric vocalizations. More complete knowledge of the Kittlitz's Murrelet vocal repertoire is needed before vocalizations can be either used or discarded in the design of effective programs to monitor this rare and poorly-known species.

Condor↗

USGS1999

Discovery of a new Kittlitz's murrelet nest: Clues to habitat selection and nest-site fidelity

On 13 June 1993, a new Kittlitz's murrelet ( Brachyramphus brevirostris ) nest was discovered near Red Mountain on the Kenai Peninsula, Alaska. The nest was on a 22° slope at about 900 m elevation with a northeast aspect, and contained a 60.2 × 40.6 mm egg that weighed 49.0 g. Downy feathers and weathered fecal material found at the nest indicated re-use from a previous year, suggesting possible nest site fidelity. The nest was located in an area scoured by winds and free of snow during early spring, suggesting that this may be an important mesoscale factor influencing selection of nesting habitat. Proximity to suitable foraging habitat, particularly sheltered bays and glacial river outflows, may affect breeding habitat choice over larger spatial scales.

Alaska↗

USGS1999

Temporal and geographic variation in fish communities of lower Cook Inlet, Alaska

Nearshore and shelf fish communities were studied in three areas of lower Cook Inlet, Alaska: the Barren Islands (oceanic and well-mixed waters), Kachemak Bay (mixed oceanic waters with significant freshwater runoff), and Chisik Island (estuarine waters). Fish were sampled with beach seines (n=413 sets) and midwater trawls (n=39 sets). We found that lower Cook Inlet supported a diverse nearshore fish community of at least 52 species. Fifty of these species were caught in Kachemak Bay, 24 at Chisik Island, and 12 at the Barren Islands. Pacific sand lance dominated Barren Islands and Kachemak Bay nearshore habitats, comprising 99% and 71% of total individuals, respectively. The nearshore Chisik Island fish community was not dominated by any one species; instead it exhibited higher diversity. These spatial differences appeared linked to local oceanographic regimes and sediment influx. Analysis of historical data revealed that the nearshore Kachemak Bay fish community changed significantly between 1976 and 1996, showing increased diversity and abundance in several taxa, notably gadids, salmonids, pleuronectids, and sculpins. Decadal differences appeared to be related to large-scale climate changes in the North Pacific. Catches of most taxa peaked in May-August, and were low during other months of the year. Several species were present for only part of the summer. Species composition of seine catches differed significantly between consecutive high and low tides, but not between consecutive sets or years. Midwater trawls took 26 species, 14 of which were present in Kachemak Bay, 19 near Chisik Island, and 7 at the Barren Islands. Community structures in shelf and nearshore waters were similar: diversity was high and abundance low at Chisik Island, whereas a few abundant species dominated at both Kachemak Bay and the Barren Islands. In addition, the low fish abundance near Chisik Island appeared to be related to declining seabird numbers at this colony.

Fishery Bulletin↗

USGS1999

Juvenile Marbled Murrelet nurseries and the productivity index

Late summer counts of juveniles at sea are used as an index of Marbled Murrelet ( Brachyramphus marmoratus ) reproductive success, but little is known about juvenile dispersal or habitat use. Further, it is not known whether these counts accurately reflect absolute breeding success. To address these questions we conducted five boat surveys for Marbled Murrelets and Pigeon Guillemots ( Cepphus columba ) in Kachemak Bay, Alaska between 7-24 August 1996. Juvenile murrelet distribution in the bay was patchy, and we identified a juvenile Marbled Murrelet 'nursery' area in the outer bay. Fifty-three of 61 juvenile murrelets were in this area, whereas after-hatch-year (AHY) murrelets were dispersed throughout the bay, as were juvenile and AHY Pigeon Guillemots. The murrelet nursery was characterized by water inside of or at the edge of a 20 m deep contour, semi-protected seas, productive waters, and a large bed of Nereocystis kelp. Juveniles comprised 16.1% of all murrelets and 24.8% of all guillemots observed at sea. These data suggest a maximum reproductive success of 0.32 chicks/pair if all AHY murrelets were breeding and 0.46 chicks/pair if only 70% of AHY murrelets were breeding. For guillemots, maximum productivity estimated from at-sea counts was 0.50 chicks/pair if all AHY were breeding and 0.71 chicks/pair if only 70% were breeding. The guillemot estimate was similar to that obtained by concurrent studies at nine guillemot colonies in the bay (0.56 chicks/pair). These results suggest that at sea surveys in late summer provide a reasonable index of local productivity for nearshore alcids. Further, if murrelet nursery areas can be found, at sea counts may provide a valid measure of absolute productivity.

Alaska↗

USGS1999

Biology of the genus Ammodytes , the sand lances

Although much taxonomic confusion exists within the genus Ammodytes , six species are currently recognized: personatus , hexapterus , americanus , dubius , tobianus , and marinus . Sand lance are both euryhaline and eurythermal, as well as tolerant of reduced oxygen concentrations. The absence of a swim bladder allows this narrow, elongate fish to spend much time buried dormant in intertidal and shallow subtidal substrates, venturing out only to feed or spawn. All Ammodytes species appear to be relatively dormant in the winter and one ( A. personatus ) also estivates during summer. Copepods are their primary food source, allowing for rapid energy accumulation during secondary production blooms. Life spans range from 3 to 12 years within the genus. Spawning usually occurs in fall or winter (although some species spawn in spring) with the production of demersal, slightly adhesive eggs. Early development is oxygen and temperature dependent. Larval sand lance hatch before spring plankton blooms and have several mechanisms to resist starvation. Density-dependent conditions are common for both adults and juveniles. Sand lance are host to a wide variety of parasites, although prevalence is unclear. Because of their abundance, schooling behavior, energetic content, and size, sand lance are an important forage species throughout their range for a wide variety of marine predators.

Book chapter↗

USGS1999

Biological effects of the 1997/98 ENSO in Cook Inlet, Alaska

We have been conducting detailed studies of the biology of seabirds in relation to oceanography and forage fish ecology in lower Cook Inlet, Alaska, since 1995. This fortuitously allowed us to document biological effects of the 1997/98 ENSO in this region. Anomalously warm sea surface temperatures (SSTs) were observed in the Gulf of Alaska (GOA) beginning in June of 1997, but not in Cook Inlet until September, 1997. Warm temperature anomalies at the surface and at depth persisted until May of 1998, when temperatures returned to average in the GOA and Cook Inlet. Thus, temperature anomalies occurred outside the core window of productivity (June–August) for forage fish and seabirds in both 1997 and 1998. Abundance or production of phytoplankton, zooplankton, fish, and seabirds in lower Cook Inlet varied among years, and overall appeared to be depressed in 1998. We observed a few biological anomalies that might be attributed to ENSO effects: (1) a significant die-off of Common Murres occurred in March–May of 1998, (2) murres and Black-legged Kittiwakes were physiologically stressed during the 1998 breeding season, (3) murres failed to reproduce at one colony in 1998, (4) kittiwake breeding success was lower than usual at colonies in 1998, and (5) phenology of breeding was later in 1998 for both murres and kittiwakes. We presume that seabird die-offs, reduced productivity and delayed phenology were linked to a reduction or delay in food availability, but the mechanism by which anomalously warm water temperatures in winter reduce forage fish availability during the summer breeding season for seabirds is not known.

Alaska↗

USGS1998

Hermit crabs in the diet of Pigeon Guillemots at Kachemak Bay, Alaska

Guillemots ( Cepphus spp.) feed their chicks a diet that is almost exclusively fish. We observed Pigeon Guillemots ( C. columba ) at two colonies in Alaska where hermit crabs (Crustacea: Anomura) were a major part of the diet for some nestlings. Hermit crabs were delivered to three of five observed nests at one colony, comprised between 2% and 22% of the items delivered at those nests, and were the second most common food type at one nest. Hermit crabs may be an attractive prey item when lipid-rich forage fish are scarce, and crabs living in gastropod shells that have been softened by encrustations of Suberites sponges may be vulnerable to guillemot predation.

Alaska↗

USGS1998

Foods of Spectacled Eiders Somateria fischeri in the Bering Sea, Alaska

The winter diet of Spectacled Eiders living in marine habitats is known only from two individuals described by Cottam (1939). Here we examine marine diets from 36 stomachs collected near St. Lawrence Island, Bering Sea, Alaska, during May-June in 1987 and 1992. All Spectacled Eiders ate Mollusca, including Gastropoda (snails; frequency of occurrence 20.0%; sole taxon 0.0%) and Bivalvia (bivalves; 80.0%; 48.0%), and Crustacea (barnacles, amphipods and crabs; 30.6%; 0.0%). One bird ate a cod. The predominant species group eaten was Macoma Clams (72.0%; 36.0%). Prey species of Spectacled Eiders occur predominantly in waters 25-60 m deep in the Bering Sea. To obtain these prey, especially the bivalves, on the winter area Spectacled Eiders must forage in waters exceeding 40 m. We speculate that Spectacled Eiders regularly forage at depths of 45-70 m throughout winter.

Alaska↗

USGS1998

Marbled murrelets have declined in Alaska

In the last issue of Northwest Science , Hayward and Iverson (“Long-Term Trends in Marbled Murrelets in Southeast Alaska Based on Christmas Bird Counts”) failed to mention other evidence for 40-75% declines in murrelet populations, or discuss implications of a climate regime shift that has reduced populations of seabirds in Alaska, or present any useful information on the status of old-growth breeding habitat for murrelets. They examined Christmas Bird Count (CBC) data from Southeast Alaska, and concluded that there is no evidence for declines in populations. They suggested that our (Piatt and Naslund 1995) previous analysis of CBC data for murrelets was erroneous, and suggested that “ the disparity between our conclusions… invites explanation ”. Invitation accepted. In the following, I will show that there was no disparity in conclusions, that Hayward and Iverson mis-represented our conclusions and they conducted a highly selective review of evidence for murrelet population changes in Alaska. The result was a paper that was inaccurate, incomplete, out-of-date, mis-leading and of little service to the readers of Northwest Science who might have read the article hoping to gain some new insight on the status of marbled murrelets in Alaska.

Alaska↗

USGS1997

Mass-mortality of guillemots ( Uria aalge ) in the Gulf of Alaska in 1993

During the first six months of 1993, about 3500 dead and moribund guillemots ( Uria aalge ) were observed throughout the northern Gulf of Alaska coast ( ca 1800 km range). Mortality peaked during March. Highest numbers were observed in western Prince William Sound and along the south coast of the Kenai Peninsula. Large flocks of live guillemots gathered in nearshore waters, in contrast to most winters when guillemots reside offshore. Most guillemots recovered were extremely emaciated ( ca 60% of normal weight) and sub-adult (80%). Based on carcass deposition and persistence experiments, we calculate that about 10 900 birds eventually came ashore on beaches that were surveyed. Even if most birds killed made it to shore, only a fraction of beaches in the Gulf of Alaska were surveyed and we estimate that a minimum total of 120 000 guillemots died. Results of other investigations on potential causes of mortality (biotoxins, pathogens, parasites, metals, etc.) were either negative or inconclusive, and necropsies lead us to believe that starvation was the proximate cause of death. Reduced food availability could have been related to anomalous sea conditions found during the prolonged 1990–1995 El Niño-Southern Oscillation event.

Alaska↗

USGS1997

Proximate composition and energy density of some North Pacific forage fishes

Mature pelagic forage fish species (capelin, sand lance, squid) had greater lipid concentrations than juvenile age-classes of large demersal and pelagic fish species (walleye pollock, Pacific cod, Atka mackerel, greenling, prowfish, rockfish, sablefish). Myctophids preyed on by puffins have at least twice as much lipid per gram compared to mature capelin, sand lance and squid, and an order of magnitude greater lipid concentrations than juvenile forage fish. Energy density of forage fishes was positively correlated with lipid content, and negatively correlated with water, ash-free lean dry mass (mostly protein), and ash contents.

Comparative Biochemistry and Physiology, Part A: M↗

USGS1997

Alternative interpretations of oil spill data

In his article "Oil, Seabirds, and Science" (BioScience 46: 587-597), John Wiens attempted to review Exxon Valdez oil spill (EVOS) damage assessment studies and the politics of EVOS science in one stroke. In my opinion, neither purpose was particularly well served.

Alaska↗