Variations in northeast Asian environments over the last 350,000 years reconstructed from pollen records from the northwest Pacific Ocean

EXTRACT (SEE PDF FOR FULL ABSTRACT): Recent analyses of terrestrial (pollen) and marine microfossils (foraminifera and radiolaria) in cores V28-204 and RC14-99 from the northwest Pacific Ocean extend the continuous, chronostratigraphically-controlled records of the regional vegetation of the Pacific coast of Japan and offshore marine environments through three full glacial cycles. The high-resolution pollen time series show systematic relationships between fluctuations in Japanese vegetation and global ice volume over the last 350 kyr. ... Comparison with solar insolation at 30°N and with an index of orbital parameters suggests that variation in northeast Asian summer monsoon intensity is related to orbital forcing.

Ecological condition of coastal ocean waters along the U.S. Western Continental Shelf: 2003

Executive Summary: The western National Coastal Assessment (NCA-West) program of EPA, in conjunction with the NOAA National Ocean Service (NOS), conducted an assessment of the status of ecological condition of soft sediment habitats and overlying waters along the western U.S. continental shelf, between the target depths of 30 and 120 m, during June 2003. NCA-West and NOAA/NOS partnered with the West Coast states (Washington (WA), Oregon (OR), and California (CA)), and the Southern California Coastal Water Research Project (SCCWRP) Bight ’03 program to conduct the survey. A total of 257 stations were sampled from Cape Flattery, WA to the Mexican border using standard methods and indicators applied in previous coastal NCA projects. A key study feature was the incorporation of a stratified-random sampling design with stations stratified by state and National Marine Sanctuary (NMS) status. Each of the three states was represented by at least 50 random stations. There also were a total of 84 random stations located within NOAA’s five NMSs along the West Coast including the Olympic Coast NMS (OCNMS), Cordell Bank NMS (CBNMS), Gulf of Farallones NMS (GFNMS), Monterey Bay NMS (MBNMS), and Channel Islands NMS (CINMS). Collection of flatfish via hook-and-line for fish-tissue contaminant analysis was successful at 50 EMAP/NCA-West stations. Through a collaboration developed with the FRAM Division of the Northwest Fisheries Science Center, fish from an additional 63 stations in the same region and depth range were also analyzed for fish-tissue contaminants. Bottom depth throughout the region ranged from 28 m to 125 m for most stations. Two slightly deeper stations from the Southern California Bight (SCB) (131, 134 m) were included in the data set. About 44% of the survey area had sediments composed of sands (< 20% silt-clay), about 47% was composed of intermediate muddy sands (20-80% silt-clay), and about 9% was composed of muds (> 80% silt-clay). The majority of the survey area (97%) had relatively low percent total organic carbon (TOC) levels of < 2%, while a small portion (< 1%) had high TOC levels (> 5%), in a range potentially harmful to benthic fauna. Salinity of surface waters for 92% of the survey area were > 31 psu, with most stations < 31 psu associated with the Columbia River plume. Bottom salinities ranged only between 31.6 and 34.4 psu. There was virtually no difference in mean bottom salinities among states or between NMS and non-NMS stations. Temperatures of surface water (range 8.5 -19.9 °C) and bottom water (range 5.8 -14.7 °C) averaged several degrees higher in CA in comparison to WA and OR. The Δσt index of watercolumn stratification indicated that about 31% of the survey area had strong vertical stratification of the water column. The index was greatest for waters off WA and lowest for CA waters. Only about 2.6 % of the survey area had surface dissolved oxygen (DO) concentrations ≤ 4.8 mg/L, and there were no values below the lower threshold (2.3 mg/L) considered harmful to the survival and growth of marine animals. Surface DO concentrations were higher in WA and OR waters than in CA, and higher in the OC NMS than in the CA sanctuaries. An estimated 94.3% of the area had bottom-water DO concentrations ≤ 4.8 mg/L and 6.6% had concentrations ≤ 2.3 mg/L. The high prevalence of DO from 2.3 to 4.8 mg/L (85% of survey area) is believed to be associated with the upwelling of naturally low DO water across the West Coast shelf. Mean TSS and transmissivity in surface waters (excluding OR due to sample problems) were slightly higher and lower, respectively, for stations in WA than for those in CA. There was little difference in mean TSS or transmissivity between NMS and non-NMS locations. Mean transmissivity in bottom waters, though higher in comparison to surface waters, showed little difference among geographic regions or between NMS and non-NMS locations. Concentrations of nitrate + nitrite, ammonium, total dissolved inorganic nitrogen (DIN) and orthophosphate (P) in surface waters tended to be highest in CA compared to WA and OR, and higher in the CA NMS stations compared to CA non-sanctuary stations. Measurements of silicate in surface waters were limited to WA and CA (exclusive of the SCB) and showed that concentrations were similar between the two states and approximately twice as high in CA sanctuaries compared to OCNMS or nonsanctuary locations in either state. The elevated nutrient concentrations observed at CA NMS stations are consistent with the presence of strong upwelling at these sites at the time of sampling. Approximately 93% of the area had DIN/P values ≤ 16, indicative of nitrogen limitation. Mean DIN/P ratios were similar among the three states, although the mean for the OCNMS was less than half that of the CA sanctuaries or nonsanctuary locations. Concentrations of chlorophyll a in surface waters ranged from 0 to 28 μg L-1, with 50% of the area having values < 3.9 μg L-1 and 10% having values > 14.5 μg L-1. The mean concentration of chlorophyll a for CA was less than half that of WA and OR locations, and concentrations were lowest in non-sanctuary sites in CA and highest at the OCNMS. Shelf sediments throughout the survey area were relatively uncontaminated with the exception of a group of stations within the SCB. Overall, about 99% of the total survey area was rated in good condition (<5 chemicals measured above corresponding effect range low (ERL) concentrations). Only the pesticides 4,4′-DDE and total DDT exceeded corresponding effect range-median (ERM) values, all at stations in CA near Los Angeles. Ten other contaminants including seven metals (As, Cd, Cr, Cu, Hg, Ag, Zn), 2-methylnaphthalene, low molecular weight PAHs, and total PCBs exceeded corresponding ERLs. The most prevalent in terms of area were chromium (31%), arsenic (8%), 2-methylnaphthalene (6%), cadmium (5%), and mercury (4%). The chromium contamination may be related to natural background sources common to the region. The 2-methylnaphthalene exceedances were conspicuously grouped around the CINMS. The mercury exceedances were all at non-sanctuary sites in CA, particularly in the Los Angeles area. Concentrations of cadmium in fish tissues exceeded the lower end of EPA’s non-cancer, human-health-risk range at nine of 50 EMAP/NCA-West and nine of 60 FRAM groundfish-survey stations, including a total of seven NMS stations in CA and two in the OCNMS. The human-health guidelines for all other contaminants were only exceeded for total PCBs at one station located in WA near the mouth of the Columbia River. Benthic species richness was relatively high in these offshore assemblages, ranging from 19 to 190 taxa per 0.1-m2 grab and averaging 79 taxa/grab. The high species richness was reflected over large areas of the shelf and was nearly three times greater than levels observed in estuarine samples along the West Coast (e.g NCA-West estuarine mean of 26 taxa/grab). Mean species richness was highest off CA (94 taxa/grab) and lower in OR and WA (55 and 56 taxa/grab, respectively). Mean species richness was very similar between sanctuary vs. non-sanctuary stations for both the CA and OR/WA regions. Mean diversity index H′ was highest in CA (5.36) and lowest in WA (4.27). There were no major differences in mean H′ between sanctuary vs. nonsanctuary stations for both the CA and OR/WA regions. A total of 1,482 taxa (1,108 to species) and 99,135 individuals were identified region-wide. Polychaetes, crustaceans and molluscs were the dominant taxa, both by percent abundance (59%, 17%, 12% respectively) and percent species (44%, 25%, 17%, respectively). There were no major differences in the percent composition of benthic communities among states or between NMSs and corresponding non-sanctuary sites. Densities averaged 3,788 m-2, about 30% of the average density for West Coast estuaries. Mean density of benthic fauna in the present offshore survey, averaged by state, was highest in CA (4,351 m-2) and lowest in OR (2,310 m-2). Mean densities were slightly higher at NMS stations vs. non-sanctuary stations for both the CA and OR/WA regions. The 10 most abundant taxa were the polychaetes Mediomastus spp., Magelona longicornis, Spiophanes berkeleyorum, Spiophanes bombyx, Spiophanes duplex, and Prionospio jubata; the bivalve Axinopsida serricata, the ophiuroid Amphiodia urtica, the decapod Pinnixa occidentalis, and the ostracod Euphilomedes carcharodonta. Mediomastus spp. and A. serricata were the two most abundant taxa overall. Although many of these taxa have broad geographic distributions throughout the region, the same species were not ranked among the 10 most abundant taxa consistently across states. The closest similarities among states were between OR and WA. At least half of the 10 most abundant taxa in NMSs were also dominant in corresponding nonsanctuary waters. Many of the abundant benthic species have wide latitudinal distributions along the West Coast shelf, with some species ranging from southern CA into the Gulf of Alaska or even the Aleutians. Of the 39 taxa on the list of 50 most abundant taxa that could be identified to species level, 85% have been reported at least once from estuaries of CA, OR, or WA exclusive of Puget Sound. Such broad latitudinal and estuarine distributions are suggestive of wide habitat tolerances. Thirteen (1.2%) of the 1,108 identified species are nonindigenous, with another 121 species classified as cryptogenic (of uncertain origin), and 208 species unclassified with respect to potential invasiveness. Despite uncertainties of classification, the number and densities of nonindigenous species appear to be much lower on the shelf than in the estuarine ecosystems of the Pacific Coast. Spionid polychaetes and the ampharetid polychaete Anobothrus gracilis were a major component of the nonindigenous species collected on the shelf. NOAA’s five NMSs along the West Coast of the U.S. appeared to be in good ecological condition, based on the measured indicators, with no evidence of major anthropogenic impacts or unusual environmental qualities compared to nearby nonsanctuary waters. Benthic communities in sanctuaries resembled those in corresponding non-sanctuary waters, with similarly high levels of species richness and diversity and low incidence of nonindigenous species. Most oceanographic features were also similar between sanctuary and non-sanctuary locations. Exceptions (e.g., higher concentrations of some nutrients in sanctuaries along the CA coast) appeared to be attributable to natural upwelling events in the area at the time of sampling. In addition, sediments within the sanctuaries were relatively uncontaminated, with none of the samples having any measured chemical in excess of ERM values. The ERL value for chromium was exceeded in sediments at the OCNMS, but at a much lower percentage of stations (four of 30) compared to WA and OR non-sanctuary areas (31 of 70 stations). ERL values were exceeded for arsenic, cadmium, chromium, 2- methylnaphthalene, low molecular weight PAHs, total DDT, and 4,4′-DDE at multiple sites within the CINMS. However, cases where total DDT, 4,4′-DDE, and chromium exceeded the ERL values were notably less prevalent at CINMS than in non-sanctuary waters of CA. In contrast, 2-methylnaphthalene above the ERL was much more prevalent in sediments at the CINMS compared to non-sanctuary waters off the coast of CA. While there are natural background sources of PAHs from oil seeps throughout the SCB, this does not explain the higher incidence of 2-methylnaphthalene contamination around CINMS. Two stations in CINMS also had levels of TOC (> 5%) potentially harmful to benthic fauna, though none of these sites exhibited symptoms of impaired benthic condition. This study showed no major evidence of extensive biological impacts linked to measured stressors. There were only two stations, both in CA, where low numbers of benthic species, diversity, or total faunal abundance co-occurred with high sediment contamination or low DO in bottom water. Such general lack of concordance suggests that these offshore waters are currently in good condition, with the lower-end values of the various biological attributes representing parts of a normal reference range controlled by natural factors. Results of multiple linear regression, performed using full model procedures to test for effects of combined abiotic environmental factors, suggested that latitude and depth had significant influences on benthic variables regionwide. Latitude had a significant inverse influence on all three of the above benthic variables, i.e. with values increasing as latitude decreased (p< 0.01), while depth had a significant direct influence on diversity (p < 0.001) and inverse effect on density (p <0.01). None of these variables varied significantly in relation to sediment % fines (at p< 0.1), although in general there was a tendency for muddier sediments (higher % fines) to have lower species richness and diversity and higher densities than coarser sediments. Alternatively, it is possible that for some of these sites the lower values of benthic variables reflect symptoms of disturbance induced by other unmeasured stressors. The indicators in this study included measures of stressors (e.g., chemical contaminants, eutrophication) that are often associated with adverse biological impacts in shallower estuarine and inland ecosystems. However, there may be other sources of humaninduced stress in these offshore systems (e.g., bottom trawling) that pose greater risks to ambient living resources and which have not been captured. Future monitoring efforts in these offshore areas should include indicators of such alternative sources of disturbance. (137pp.) (PDF contains 167 pages)

The economic importance of marine angler expenditures in the United States.

In 1998, the National Marine Fisheries Service (NMFS) began a series of marine angler expenditure surveys in the coastal regions of the United States (U.S.) to evaluate marine recreational fishing expenditures and the financial impacts of these expenditures in each region and the U.S. as a whole. In this report, we use the previously estimated expenditure estimates to assess the total financial impact of anglers’ saltwater expenditures. Estimates are provided for sales, income, employment, and tax impacts for each coastal state in the U.S. Aggregate estimates are also provided for the entire U.S., excluding Alaska, Hawaii, and Texas. Direct, indirect, and induced effects associated with resident and non-resident angler expenditures were estimated using a regional input-output modeling system called IMPLAN Pro. Nationwide, recreational saltwater fishing generated over $30.5 billion in sales in 2000, nearly $12.0 billion in income, and supported nearly 350,000 jobs. Approximately 89 cents of every dollar spent by saltwater anglers was estimated to remain within the U.S. economy. At the state level, many of the goods anglers purchased were imports, and, as such, as little as 44 cents of every dollar stayed in Rhode Island and as much as 80 cents of every dollar stayed in Georgia. In the Northeast, the highest impacts were generated in New Jersey, even though recreational fishing expenditures in Massachusetts and Maryland were considerably higher. In the Southeast, the highest impacts were generated in Florida, and on the Pacific Coast, the highest impacts were generated in California. Expenditures on boat maintenance/expenses generated more impacts than any other expenditure category in the U.S. Expenditures on rods and reels was the single most important expense category in terms of generating impacts in most of the Northeast states. Expenditures on boat expenses generated the highest in most Southeast states, and expenditures for boat accessories produced the highest impacts in most Pacific Coast states.(PDF file contains 184 pages.)

Description of Early Larvae of Four Northern California Species of Rockfishes (Scorpaenidae: Sebastes) from Rearing Studies

About 72 species of Sebastes (Family Scorpaenidae) are found along the eastern Pacific coast of North America, some of which are heavily exploited by both commercial and sport fisheries. Because of the large number of species, the identification of early life stages has progressed slowly. The objectives of this study were 1) to rear the larvae of four species of rockfish (Sebastes mystinus, S. carnatus, S. atrovirens, and S. rastrelliger); and 2) to describe the larvae using morphometric measurements, pigmentation patterns, and head spination. Pigmentation was the most useful feature for identification purposes. Two general patterns were found: 1) a short row of ventral midline melanophores on the tail, and none or very little postero-dorsal pigmentation (S. mystinus); and 2) complete ventral midline pigmentation on the tail, and anterior and postero-dorsal melanophores (S. carnatus, S. atrovirens, and S. rastrelliger). With the exception of very early stages of S. carnatus and S. atrovirens, these species can be readily identified. Morphometric proportions and head spination did not show major differences among species. Because of the great similarities found among species in this genus, descriptions from field studies are uncertain to some extent. Laboratory rearings, although difficult, can at least provide early larvae from known species which allow precise identification as well as an estimation ofvariability of characters (e.g., pigmentation) within and between broods.(PDF file contains 22 pages.)

Widow rockfish: Proceedings of a workshop, Tiburon, California, December 11-12, 1980

This workshop was organized because of the increase between 1978 and 1980 in coastwide landings of widow rockfish, from less than 1,000 mt to more than 20,000 mt, and because of scientists' concern with the lack of knowledge both of the fishery and biology of the species. Most scientists active in research on Pacific groundfish, as well as some members of the fishing industry and fishery managers, attended the workshop. These proceedings contain the report of the workshop discussion panel, status reports on California, Oregon, and Washington fisheries through 1980, and a collection of seven papers presented at the workshop. The status reports provide an historical perspective of the development of an important fishery. The papers present a fairly complete survey of biological knowledge of widow rockfish, economic status of the fishery, and fishery-independent methods for estimation of abundance. The papers also contain some information developed after the workshop. Since the workshop, the fishery has matured. Largest landings were made in 1981, when more than 28,000 mt were landed. Maximum sustainable yield (MSY) is estimated to be slightly less than 10,000 mt, and the stock appeared to be at about the MSY level in 1985. The Pacific Fishery Management Council and National Marine Fisheries Service have implemented regulations that have maintained landings since 1983 at approximately the maximum sustainable yield level. Fishery-dependent stock assessments are being made on an annual basis for the Pacific Fishery Management Council. While these assessments are considered to be the best possible with available data, scientists responsible for the assessment have chosen to delay their publication in the formal scientific literature until more data are obtained. However, the stock assessment reports are available from the Pacific Fishery Management Council. In addition to the papers in this collection, three papers have been published on widow rockfish since 1980. BoehIert, Barss, and Lamberson (1982) estimate fecundity of the species off Oregon; Gunderson (1984) describes the fishery and management actions; and Laroche and Richardson (1981) describe the morphology and distribution of juvenile widow rockfish off Oregon. During the past decade, the fishery for widow rockfish has developed from a minor fishery to one of the more important on the Pacific Coast. Our knowledge of the biology and dynamics of the species has progressed from minimal to relatively extensive for a groundfish species. It is our intention in preparing this collection of papers to make this knowledge readily available to the scientific community. (PDF file contains 63 pages.)

Observations on the taxonomy, biology, and ecology of the Engraulid and Clupeid fishes in the Gulf of Nicoya, Costa Rica.

ENGLISH: In 1952 and 1953, during the course of a study of the abrupt decline and apparent disappearance from the Gulf of Nicoya of the population of anchovetas (Cetengraulis mysticetus), an important tuna bait fish, considerable material was collected on the taxonomy, biology, and ecology of the several anchovies and the herrings inhabith1g the Gulf. The Gulf of Nicoya, approximately 50 miles long and varying in width from about 5 to 35 miles, is located on the Pacific coast of Costa Rica. The family Engraulididae is represented by four genera comprising fourteen species, and nine species were identified as members of eight genera of the family Clupeidae. All of the species inhabit other coastal areas of the tropical Eastern Pacific. SPANISH: En 1952 Y 1953, durante el curso de un estudio sobre la declinación abrupta y la aparente desaparición en el Golfo de Nicoya de la población de anchovetas (Cetengraulis mysticetus) un pez de importancia para la pesca del atún, se recolectó material considerable relacionado con la taxonomía, biología y ecología de las diversas especies de anchoas y arenques que habitan dicho Golfo. El Golfo de Nicoya, que mide aproximadamente 50 millas de largo y varía en su anchura entre 5 y 35 millas, se encuentra en la costa del Pacífico de Costa Rica. La familia de los Engráulidos está representada por cuatro géneros que comprenden catorce especies, y otras nueve fueron identificadas como miembros de ocho géneros de la familia Clupeidae. Todas estas especies habitan otras áreas costeras del Pacífico Oriental tropical. (PDF contains 144 pages.)

Towed vehicles: undulating platforms as tools for maping coastal processes and water quality assessment, Seaside, California, February 5-7,2007. Workshop proceedings

The Alliance for Coastal Technologies (ACT) Workshop on Towed Vehicles: Undulating Platforms As Tools for Mapping Coastal Processes and Water Quality Assessment was convened February 5-7,2007 at The Embassy Suites Hotel, Seaside, California and sponsored by the ACT-Pacific Coast partnership at the Moss Landing Marine Laboratories (MLML). The TUV workshop was co-chaired by Richard Burt (Chelsea Technology Group) and Stewart Lamerdin (MLML Marine Operations). Invited participants were selected to provide a uniform representation of the academic researchers, private sector product developers, and existing and potential data product users from the resource management community to enable development of broad consensus opinions on the application of TUV platforms in coastal resource assessment and management. The workshop was organized to address recognized limitations of point-based monitoring programs, which, while providing valuable data, are incapable of describing the spatial heterogeneity and the extent of features distributed in the bulk solution. This is particularly true as surveys approach the coastal zone where tidal and estuarine influences result in spatially and temporally heterogeneous water masses and entrained biological components. Aerial or satellite based remote sensing can provide an assessment of the aerial extent of plumes and blooms, yet provide no information regarding the third dimension of these features. Towed vehicles offer a cost-effective solution to this problem by providing platforms, which can sample in the horizontal, vertical, and time-based domains. Towed undulating vehicles (henceforth TUVs) represent useful platforms for event-response characterization. This workshop reviewed the current status of towed vehicle technology focusing on limitations of depth, data telemetry, instrument power demands, and ship requirements in an attempt to identify means to incorporate such technology more routinely in monitoring and event-response programs. Specifically, the participants were charged to address the following: (1) Summarize the state of the art in TUV technologies; (2) Identify how TUV platforms are used and how they can assist coastal managers in fulfilling their regulatory and management responsibilities; (3) Identify barriers and challenges to the application of TUV technologies in management and research activities, and (4) Recommend a series of community actions to overcome identified barriers and challenges. A series of plenary presentation were provided to enhance subsequent breakout discussions by the participants. Dave Nelson (University of Rhode Island) provided extensive summaries and real-world assessment of the operational features of a variety of TUV platforms available in the UNOLs scientific fleet. Dr. Burke Hales (Oregon State University) described the modification of TUV to provide a novel sampling platform for high resolution mapping of chemical distributions in near real time. Dr. Sonia Batten (Sir Alister Hardy Foundation for Ocean Sciences) provided an overview on the deployment of specialized towed vehicles equipped with rugged continuous plankton recorders on ships of opportunity to obtain long-term, basin wide surveys of zooplankton community structure, enhancing our understanding of trends in secondary production in the upper ocean. [PDF contains 32 pages]

Oceanographic Profiling and Spectroradiometer Observations from the MOCE-2 Cruise: 28 March to 14 April 1993

This report contains results from the second cruise of the Modis Optical Characterization Experiment (MOCE). Data presented here were obtained on the Mexican Research Vessel El Puma between 29 March and 13 April along the Pacific coast of Baja California and in the Gulf of California. Three types of data are reported: high spectral resolution radiometry at three depths for 13 stations; salinity, temperature beam attenuation and chlorophyll-a fluorescence, profiles at the same stations; and total suspended matter and suspended organic carbon and nitrogen.(PDF is 90 pages.)

Hypoxic and low pH water in the nearshore marine environments of Monterey Bay, California: characterizing a decade of oxygen and pH, and drivers of variability.

A decade-long time series recorded in southern Monterey Bay, California demonstrates that the shallow, near-shore environment (17 m depth) is regularly inundated with pulses of cold, hypoxic and low pH water. During these episodes, oxygen can drop to biologically threatening levels, and pH levels were lower than expected. Weekly water chemistry monitoring revealed that the saturation state of aragonite (the more soluble form of calcium carbonate) was often below saturation and had a moderate positive relationship with pH, however, analytical and human error could be high. Pulses of hypoxia and low pH water with the greatest intensity arise at the onset of the spring upwelling season, and fluctuations are strongly semidurnal (tidal) and diurnal. Arrival of cold, hypoxic water on the inner shelf typically occurs 3 days after the arrival of a strong upwelling event and appears to be driven by upwelling modulated by internal tidal fluctuations. I found no relationship between the timing of low-oxygen events and the diel solar cycle nor with terrestrial nutrient input. These observations are consistent with advection of hypoxic water from the deep, offshore environment where water masses experience a general decline of temperature, oxygen and pH with depth, and inconsistent with biochemical forcing. Comparisons with concurrent temperature and oxygen time series taken ~20 km away at the head of the Monterey Canyon show similar patterns but even more intense hypoxic events due to stronger semidiurnal forcing there. Analysis of the durations of exposure to low oxygen levels establishes a framework for assessing the ecological relevance of these events. Increasing oceanic hypoxia and acidification of both surface and deep waters may increase the number, intensity, duration and spatial extent of future intrusions along the Pacific coast. Evaluation of the resiliency of nearshore ecosystems such as kelp forests, rocky reefs and sandy habitats, will require consideration of these events.

Assessment of habitat quality for juvenile California halibut (Paralichthys californicus) in a seasonally arid estuary

We evaluated habitat quality for juvenile California halibut (Paralichthys californicus) in a Pacific Coast estuary lacking in strong salinity gradients by examining density, recent otolith growth rates, and gut fullness levels of wild-caught and caged juveniles for one year. Juveniles <200 mm standard length were caught consistently in the inner, central, and outer sections of the estuary. The density of juveniles was two times higher in the inner estuary during most of the year, consistent with active habitat selection by part of the population. A generalized linear model indicated temperature, sampling time, and the interaction between salinity and temperature were significantly related to density. However, the model explained only 21% of the variance. Gut fullness levels of wild-caught juveniles were highest during the summer, but recent otolith growth rates were not related to temperature. The proportion of individuals feeding successfully indicated that seasonal differences in food availability are more important than spatial variation in prey abundance in driving feeding success. Feeding success of caged fishes was limited, precluding the use of growth rates as indicators of local habitat quality. However, marginal increment widths were reliable indicators of somatic growth at low growth rates over two-week periods. The relatively high growth rates and abundance of small wild-caught juveniles found throughout the estuary indicates that the entire estuary system has the potential for serving as nursery habitat.

Geographical differences in the feeding patterns of red rockfish (Sebastes capensis) along South American coasts

Feeding habits and feeding strategy of red rockfish (Sebastes capensis) were studied from fish captured along most of the range of this species in coastal waters of South America. Stomach contents of 613 individuals, collected during 2003, were analyzed. Fish were obtained from six locations along the Chilean (23°S to 46°S) and Argentinian (43°S) coasts. The main prey items were Mysidacea (75.06% IRI), Osteichthyes (6.29% IRI),and Rhynchocinetes typus (6.03% IRI). Predator sex and size did not significantly affect the diet, but significant differences were found between locations. Four geographical areas, discriminated by prey occurrence and frequencies, were determined: three on the Pacific coast and one on the Atlantic coast. These areas correspond roughly with biogeographic zones described for the Chilean and southern Argentinian coasts. The feeding strategy index (FSI) indicated a specialized feeding strategy for S. capensis for most of its range. However, the FSI does not include the behaviour of a predator, and the FSI must be interpreted carefully for fishes like S. capensis that are passive ambush feeders. The abundance and availability of different prey may explain both the geographic differences in dietary composition and the specialized feeding strategy of S. capensis.

Potential use of offshore marine structures in rebuilding an overfished rockfish species, bocaccio (Sebastes paucispinis)

Although bocaccio (Sebastes paucispinis) was an economically important rockfish species along the west coast of North America, overfishing has reduced the stock to about 7.4% of its former unfished population. In 2003, using a manned research submersible, we conducted fish surveys around eight oil and gas platforms off southern California as part of an assessment of the potential value of these structures as fish habitat. From these surveys, we estimated that there was a minimum of 430,000 juvenile bocaccio at these eight structures. We determined this number to be about 20% of the average number of juvenile bocaccio that survive annually for the geographic range of the species. When these juveniles become adults, they will contribute about one percent (0.8%) of the additional amount of fish needed to rebuild the Pacific Coast population. By comparison, juvenile bocaccio recruitment to nearshore natural nursery grounds, as determined through regional scuba surveys, was low in the same year. This research demonstrates that a relatively small amount of artificial nursery habitat may be quite valuable in rebuilding an overfished species.

Hatching date, nursery grounds, and early growth of juvenile walleye pollock (Theragra chalcogramma) off northern Japan*

Walleye pollock (Theragra chalcogramma) is widely distributed in the North Pacific Ocean and plays an important role in coastal subarctic ecosystems. The Japanese Pacific population of this species is one of the most important demersal fishes for commercial fisheries in northern Japan. The population is distributed along the Pacific coast of Hokkaido and the Tohoku area (Fig. 1), which is the southern limit of distribution of the species in the western North Pacific. In Funka Bay, the main spawning ground for this population, pollock spawn from December to March (Kendall and Nakatani, 1992). Planktonic eggs and larvae are transported into the bay, where juveniles usually remain until late July when they reach 60−85 mm in total length (Hayashi et al., 1968; Nakatani and Maeda, 1987). These juvenile pollock then migrate from Funka Bay eastward to the Doto area off southeastern Hokkaido (Honda et al., 2004). Many studies on eggs, larvae, and juveniles of the species have been conducted in or near Funka Bay, but little information is available on the ecology of the early life stages in the Tohoku area. Hashimoto and Ishito (1991) suggested that eggs are transported from Funka Bay southward to the Tohoku area by the coastal branch of the Oyashio Current, but there has been no study to verify this hypothesis.

Diet composition of fish species from the southern continental shelf of Colombia

The diet composition of 30 fish species belonging to 16 families from the Pacific Coast of Colombia is described. Benthic crustaceans (37.5%) and bony fishes (23.7%, chiefly demersal) were the most important food items for the fish species analyzed. Data on diet composition of the fish species are presented for the first time which can be a source of information for trophic modeling.

Feeding habits of the dwarf weakfish (Cynoscion nannus) off the coasts of Jalisco and Colima, Mexico

Sciaenids from the Pacific coast of Mexico are used as a second-class fish species for human consumption (Aguilar-Palomino et al., 1996). The dwarf weakfish (Cynoscion nannus) (Castro-Aguirre and Arvizu-Martínez, 1976) is often caught as bycatch in the shrimp fishery but, because of its small size (<27 cm TL, total length), it is not considered a valuable resource. This species can be found in great numbers in waters between 100 and 812 m (Allen and Robertson, 1994; Fischer et al., 1995) associated with the soft-bottom regions off the coast of Jalisco and Colima (González-Sansón et al., 1997).