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)

Cruise Report 72-S-5: Inshore fisheries habitat evaluation and monitoring

(PDF contains 3 pages.)

Guidance for benthic habitat mapping: an aerial photographic approach

This document, Guidance for Benthic Habitat Mapping: An Aerial Photographic Approach, describes proven technology that can be applied in an operational manner by state-level scientists and resource managers. This information is based on the experience gained by NOAA Coastal Services Center staff and state-level cooperators in the production of a series of benthic habitat data sets in Delaware, Florida, Maine, Massachusetts, New York, Rhode Island, the Virgin Islands, and Washington, as well as during Center-sponsored workshops on coral remote sensing and seagrass and aquatic habitat assessment. (PDF contains 39 pages) The original benthic habitat document, NOAA Coastal Change Analysis Program (C-CAP): Guidance for Regional Implementation (Dobson et al.), was published by the Department of Commerce in 1995. That document summarized procedures that were to be used by scientists throughout the United States to develop consistent and reliable coastal land cover and benthic habitat information. Advances in technology and new methodologies for generating these data created the need for this updated report, which builds upon the foundation of its predecessor.

Seagrass and Aquatic Habitat Assessment Workshop Summary

Seagrass communities are among the richest and most productive, photoautotrophic coastal systems in the world. They protect and improve water quality, provide shoreline stabilization, and are important habitats for an array of fish, birds, and other wildlife. Hence, much can be gained by protecting and restoring these important living resources. Human’s impact on these vital resources from population growth, pollution, and physical damage from boating and other activities can disrupt the growth of these seagrasses communities and have devastating effects on their health and vitality. Inventory and monitoring are required to determine the dynamics of seagrasses and devise better protection and restoration for these rich resources. The purpose of this seagrass workshop, sponsored by NOAA’s CSC , USGS, and FMRI, was to move toward greater objectivity and accuracy in seagrass mapping and monitoring. This workshop helped foster interaction and communication among seagrass professionals. In order to begin the process of determining the best uniform mapping process for the biological research community. Increasing such awareness among the seagrass and management communities, it is hoped that an improved understanding of the monitoring and mapping process will lead to more effective and efficient preservation os submerged aquatic vegetation. (PDF contains 20 pages)

Survey report of NOAA Ship McArthur II cruises AR-04-04, AR-05-05 and AR-06-03: Habitat classification of side scan sonar imagery in support of deep-sea coral/sponge explorations at the Olympic Coast National Marine Sanctuary

Habitat mapping and characterization has been defined as a high-priority management issue for the Olympic Coast National Marine Sanctuary (OCNMS), especially for poorly known deep-sea habitats that may be sensitive to anthropogenic disturbance. As a result, a team of scientists from OCNMS, National Centers for Coastal Ocean Science (NCCOS), and other partnering institutions initiated a series of surveys to assess the distribution of deep-sea coral/sponge assemblages within the sanctuary and to look for evidence of potential anthropogenic impacts in these critical habitats. Initial results indicated that remotely delineating areas of hard bottom substrate through acoustic sensing could be a useful tool to increase the efficiency and success of subsequent ROV-based surveys of the associated deep-sea fauna. Accordingly, side scan sonar surveys were conducted in May 2004, June 2005, and April 2006 aboard the NOAA Ship McArthur II to: (1) obtain additional imagery of the seafloor for broader habitat-mapping coverage of sanctuary waters, and (2) help delineate suitable deep-sea coral/sponge habitat, in areas of both high and low commercial-fishing activities, to serve as sites for surveying-in more detail using an ROV on subsequent cruises. Several regions of the sea floor throughout the OCNMS were surveyed and mosaicked at 1-meter pixel resolution. Imagery from the side scan sonar mapping efforts was integrated with other complementary data from a towed camera sled, ROVs, sedimentary samples, and bathymetry records to describe geological and biological (where possible) aspects of habitat. Using a hierarchical deep-water marine benthic classification scheme (Greene et al. 1999), we created a preliminary map of various habitat polygon features for use in a geographical information system (GIS). This report provides a description of the mapping and groundtruthing efforts as well as results of the image classification procedure for each of the areas surveyed. (PDF contains 60 pages.)

Habitat mapping effort at the Olympic Coast National Marine Sanctuary – Current status and future needs

With elevating interest to establish conservation efforts for groundfish stocks and continued scrutiny over the value of marine protected areas along the west coast, the importance of enhancing our knowledge of seabed characteristics through mapping activities is becoming increasingly more important, especially in a timely manner. Shortly after the inception of the Seabed Mapping Initiative instituted with the US Geological Survey (USGS), the National Marine Sanctuary Program (NMSP) assembled a panel of habitat mapping experts. They determined that the status of existing data sets and future data acquisition needs varied widely among the individual sanctuaries and that more detailed site assessments were needed to better prioritize mapping efforts and outline an overall joint strategy. To assist with that specific effort and provide pertinent information for the Olympic Coast National Marine Sanctuary’s (OCNMS) Management Plan Review, this report summarizes the mapping efforts that have taken place at the site to date; calculates a timeframe for completion of baseline mapping efforts when operating under current data acquisition limitations; describes an optimized survey strategy to dramatically reduce the required time to complete baseline surveying; and provides estimates for the needed vessel sea-days (DAS) to accomplish baseline survey completion within a 2, 5 and 10 year timeframe. (PDF contains 38 pages.)

Olympic Coast National Marine Sanctuary Habitat Mapping: Survey report and classification of side scan sonar data from surveys HMPR-114-2004-02 and HMPR-116-2005-01.

The Olympic Coast National Marine Sanctuary (OCNMS) continues to invest significant resources into seafloor mapping activities along Washington’s outer coast (Intelmann and Cochrane 2006; Intelmann et al. 2006; Intelmann 2006). Results from these annual mapping efforts offer a snapshot of current ground conditions, help to guide research and management activities, and provide a baseline for assessing the impacts of various threats to important habitat. During the months of August 2004 and May and July 2005, we used side scan sonar to image several regions of the sea floor in the northern OCNMS, and the data were mosaicked at 1-meter pixel resolution. Video from a towed camera sled, bathymetry data, sedimentary samples and side scan sonar mapping were integrated to describe geological and biological aspects of habitat. Polygon features were created and attributed with a hierarchical deep-water marine benthic classification scheme (Greene et al. 1999). For three small areas that were mapped with both side scan sonar and multibeam echosounder, we made a comparison of output from the classified images indicating little difference in results between the two methods. With these considerations, backscatter derived from multibeam bathymetry is currently a costefficient and safe method for seabed imaging in the shallow (<30 meters) rocky waters of OCNMS. The image quality is sufficient for classification purposes, the associated depths provide further descriptive value and risks to gear are minimized. In shallow waters (<30 meters) which do not have a high incidence of dangerous rock pinnacles, a towed multi-beam side scan sonar could provide a better option for obtaining seafloor imagery due to the high rate of acquisition speed and high image quality, however the high probability of losing or damaging such a costly system when deployed as a towed configuration in the extremely rugose nearshore zones within OCNMS is a financially risky proposition. The development of newer technologies such as intereferometric multibeam systems and bathymetric side scan systems could also provide great potential for mapping these nearshore rocky areas as they allow for high speed data acquisition, produce precisely geo-referenced side scan imagery to bathymetry, and do not experience the angular depth dependency associated with multibeam echosounders allowing larger range scales to be used in shallower water. As such, further investigation of these systems is needed to assess their efficiency and utility in these environments compared to traditional side scan sonar and multibeam bathymetry. (PDF contains 43 pages.)

Benthic habitat mapping in the Olympic Coast National Marine Sanctuary: Classification of side scan sonar data from survey HMPR-108-2002-01: Version I

In September 2002, side scan sonar was used to image a portion of the sea floor in the northern OCNMS and was mosaiced at 1-meter pixel resolution using 100 kHz data collected at 300-meter range scale. Video from a remotely-operated vehicle (ROV), bathymetry data, sedimentary samples, and sonar mapping have been integrated to describe geological and biological aspects of habitat and polygon features have been created and attributed with a hierarchical deep-water marine benthic classification scheme (Greene et al. 1999). The data can be used with geographic information system (GIS) software for display, query, and analysis. Textural analysis of the sonar images provided a relatively automated method for delineating substrate into three broad classes representing soft, mixed sediment, and hard bottom. Microhabitat and presence of certain biologic attributes were also populated into the polygon features, but strictly limited to areas where video groundtruthing occurred. Further groundtruthing work in specific areas would improve confidence in the classified habitat map. (PDF contains 22 pages.)

Juvenile and small resident fishes of Florida Bay, a critical habitat in the Everglades National Park, Florida

This compendium presents information on the life history, diet, and abundance and distribution of 46 of the more abundant juvenile and small resident fish species, and data on three species of seagrasses in Florida Bay, Everglades National Park. Abundance and distribution of fish data were derived from three sampling schemes: (1) an otter trawl in basins (1984–1985, 1994–2001), (2) a surface trawl in basins (1984–1985), and (3) a surface trawl in channels (1984–1985). Results from surface trawling only included pelagic species. Collections made with an otter trawl in basins on a bi-monthly basis were emphasized. Nonparametric statistics were used to test spatial and temporal differences in the abundance of species and seagrasses. Fish species accounts were presented in four sections – Life history, Diet, Abundance and distribution, and Length-frequency distributions. Although Florida Bay is a subtropical estuary, the majority of fish species (76%) had warm-temperate affinities; i.e., only 24% were solely tropical species. The five most abundant species collected, in descending order, by (1) otter trawl in basins were: Eucinostomus gula, Lucania parva, Anchoa mitchilli, Lagodon rhomboides, and Syngnathus scovelli; (2) surface trawl in basins were: Hyporhamphus unifasciatus, Strongylura notata, Chriodorus atherinoides, Anchoa hepsetus, and Atherinomorus stipes; (3) surface trawl in channels were: Hypoatherina harringtonensis, A. stipes, A. mitchelli, H. unifasciatus, and C. atherinoides. (PDF file contains 219 pages.)

Acoustic signatures of the seafloor: Tools for predicting grouper habitat

Groupers are important components of commercial and recreational fisheries. Current methods of diver-based grouper census surveys could potentially benefit from development of remotely sensed methods of seabed classification. The goal of the present study was to determine if areas of high grouper abundance have characteristic acoustic signatures. A commercial acoustic seabed mapping system, QTC View Series V, was used to survey an area near Carysfort Reef, Florida Keys. Acoustic data were clustered using QTC IMPACT software, resulting in three main acoustic classes covering 94% of the area surveyed. Diver-based data indicate that one of the acoustic classes corresponded to hard substrate and the other two represented sediment. A new measurement of seabed heterogeneity, designated acoustic variability, was also computed from the acoustic survey data in order to more fully characterize the acoustic response (i.e., the signature) of the seafloor. When compared with diver-based grouper census data, both acoustic classification and acoustic variability were significantly different at sites with and without groupers. Sites with groupers were characterized by hard bottom substrate and high acoustic variability. Thus, the acoustic signature of a site, as measured by acoustic classification or acoustic variability, is a potentially useful tool for stratifying diver sampling effort for grouper census.

An examination of fluctuations in the “concentration index” of purse seiners and baitboats in the fishery for tropical tunas in the Eastern Pacific, 1951-1961

ENGLISH: In the eastern Pacific Ocean nearly all of the commercial catches of yellowfin tuna (Thunnus albacares) and skipjack (Katsuwonus pelamis) are taken by two types of vessels, baitboats, which use pole and line in conjunction with live-bait, and purse-seiners. From its inception until very recently (1959), this fishery was dominated by baitboats. This method of fishing has been described by Godsil (1938) and Shimada and Schaefer (1956). From 1951 through 1958 baitboats caught between 66.4 and 90.8 per cent of the yellowfin and between 87.2 and 95.3 per cent of the skipjack landed by the California-based fleet. These vessels fished for tuna throughout the year and covered virtually all of the area from southern California to northern Chile. The purse-seine fishery for tunas developed out of the round-haul net fisheries for California sardines and other species. Scofield (1951) gives a detailed description of the development of gear and fishing methods. Prior to 1959 many of the seiners engaged in other fisheries during the fall and early winter months and consequently most of the fishing effort for tuna occurred in the period February-August. The vessels were quite small, averaging approximately 120 tons carrying capacity (Broadhead and Marshall, 1960), in comparison to the baitboats, of which the most numerous size-class was 201-300 tons. The seiners were naturally more restricted in range than the baitboats and most of their effort was restricted to the northern grounds. During the period 1959-61 most of the large baitboats were converted for purse-seining and the existing seiner fleet was modernized. These developments increased the range of the seiner fleet and resulted in a wider and more nearly even spatial and temporal distribution of effort. By the early part of 1961, the purse-seine fleet approximated the level of the preconversion baitboat fleet in amount of effort applied and area covered. The changes in the purse-seine fishery and the fishing methods employed in the modernized fleet are described by Orange and Broadhead (1959), Broadhead and Marshall (1960), McNeely (1961) and Broadhead (1962). The change in the relative importance of the two gears is illustrated by the decline in the proportion of the total logged tonnage landed by California-based baitboats, in comparison to the proportion landed by seiners. In 1959 baitboats landed 49.5 per cent of the yellowfin and 87.8 per cent of the skipjack. In 1960 these percentages were 22.9 and 74.7 respectively and in 1961 the decline continued to 12.6 per cent of the yellowfin and 30.0 per cent of the skipjack (Schaefer, 1962). In previous Bulletins of this Commission (Griffiths, 1960; Calkins, 1961) the baitboat catch and effort statistics were used to compute two indices of population density and an index of concentration of fishing effort and the fluctuations of these indices were analyzed in some detail. Due to the change in the relative importance of the two gears it is appropriate to extend this investigation to include the purse-seine data. The objectives of this paper are to compute two indices of population density and an index of concentration of fishing effort and to examine the fluctuations in these indices before and after the changes in the fishery. A further objective is to compare the purse-seine indices with those of the baitboats for the same time periods. SPANISH: En el Océano Pacífico Oriental casi todas las capturas comerciales del atún aleta amarilla (Thunnus albacares) y del barrilete (Katsuwonus pelamis) son efectuadas por dos tipos de barcos, los barcos de carnada que emplean la caña y el anzuelo en conjunto con la carnada viva, y los barcos rederos. Desde su comienzo hasta hace poco tiempo (1959), esta pesquería estaba dominada por los barcos de carnada. El método de pesca usado por estos barcos ha sido descrito por Godsil (1938) y por Shimada y Schaefer (1956). De 1951 a 1958, los barcos de carnada pescaron entre el 66.4 y el 90.8 por ciento del atún aleta amarilla y entre el 87.2 y el 95.3 por ciento del barrilete descargados por la flota que tiene su base en California. Estos barcos pescaron atún durante todo el año y cubrieron virtualmente toda el área de California meridional hasta la parte norte de Chile. La pesquería del atún con redes de cerco se originó en las pesquerías de las sardinas de California y otras especies, con redes que se remolcaban circularmente. Scofield (1951) dá una descripción detallada del desarrollo de los métodos y del equipo de pesca. Antes de 1959 muchos de los rederos se dedicaban a otras pesquerías durante los meses del otoño y a principios del invierno y consecuentemente, la mayor parte del esfuerzo depesca para la producción del atún ocurría en el período febrero-agosto. Las embarcaciones eran bastante pequeñas, con un promedio de aproximadamente 120 toneladas de capacidad para el transporte (Broadhead y Marshall, 1960) en comparación con los barcos de carnada, de los cuales la clase de tamaño más numerosa era de 201 a 300 toneladas. Los rederos estaban naturalmente más restringidos en su radio de acción que los barcos de carnada y la mayor parte de su esfuerzo se limitaba a las localidades del norte. Durante el período 1959-61, la mayoría de los grandes barcos de carnada fueron convertidos al sistema de pesca con redes de cerco, y se modernizó la flota existente de los rederos. Estos cambios aumentaron el alcance de la flota de los barcos rederos dando como resultado una distribución más amplia y casi más uniforme del esfuerzo espaciado y temporal. En la primera parte del año 1961, la flota de rederos se aproximó al nivel de la preconversión de la flota de clipers, en la cantidad de esfuerzo aplicado y al área comprendida. Los cambios en la pesquería con red y los métodos de pesca empleados en la flota modernizada, han sido descritos por Orange y Broadhead (1959), Broadl1ead y Marshall (1960), McNeely (1961) y Broadhead (1962). El cambio en la importancia relativa de los dos sistemas de pesca está ilustrado por la declinación en la proporción del tonelaje total registrado, como descargado por los barcos de carnada que tienen su base en California, comparado con la proporción desembarcada por los barcos rederos. En 1959 los clipers descargaron el 49.5 por ciento del atún aleta amarilla y el 87.8 por ciento del barrilete. En 1960 estos porcentajes fueron del 22.9 y 74.7 respectivamente, y en 1961 continuó la reducción hasta el 12.6 por ciento del atún aleta amarilla y el 30.0 por ciento del barrilete (Schaefer, 1962). En Boletines anteriores de la Comisión (Griffiths, 1960; Calkins, 1961) las estadísticas de la pesca y el esfuerzo de los clipers se utilizaron para computar dos índices de la densidad de población y un índice de la concentración del esfuerzo de pesca, y se analizaron algo detalladamente las fluctuaciones de estos índices. Debido al cambio en la importancia relativa de los dos sistemas de pesca, es conveniente extender esta investigación para incluir los datos correspondientes a los barcos rederos. Los objetivos del presente estudio son de computar dos índices de la densidad de población y un índice de la concentración del esfuerzo de pesca, y examinar las fluctuaciones en estos índices, antes y después de los cambios en la pesquería. Otro objetivo es de comparar los índices de los barcos rederos, con aquellos de los clipers en los mismos períodos de tiempo.

Southeastern U.S. Deepwater Reef Fish Assemblages, Habitat Characteristics, Catches, and Life History Summaries

There are 19 economically important reef fish species in the deepwater (l00-300 m) fishery of the southeastern United States. Five species make up the majority (over 97% by weight) of the catch. In descending order of total landings for 1995, they are: tilefish, Lopholatilus chamaeleonticeps, snowy grouper, Epinephelus niveatus, blueline tilefish, Caulolatilus microps, warsaw grouper, Epinephelus nigritus, and yellowedge grouper, E. flavolimbatus. Life history summaries and estimates of catches from 1972 through 1995 for 14 species are described. (PDF file contains 45 pages.)

Benthic macrofauna and habitat monitoring on the Continental Shelf of the northeastern United States: I. Biomass

Information on long-term temporal variability of and trends in benthic community-structure variables, such as biomass, is needed to estimate the range of normal variability in comparison with the effects of environmental change or disturbance. Fishery resource distribution and population growth will be influenced by such variability. This study examines benthic macrofaunal biomass and related data collected annually between 1978 and 1985 at 27 sites on the continental shelf of the northwestern Atlantic, from North Carolina to the southern Gulf of Maine. The study was expanded at several sites with data from other studies collected at the same sites prior to 1978. Results indicate that although there was interannual and seasonal variability, as expected, biomass levels over the study period showed few clear trends. Sites exhibiting trends were either in pollution-stressed coastal areas or influenced by the population dynamics of one or a few species, especially echinoderms. (PDF file contains 34 pages.)

Species composition, distribution, and relative abundance of fishes in the coastal habitat off the southeastern United States

Ichthyofauna of the coastal «10 m depth) habitat of the South Atlantic Bight were investigated between Cape Fear, North Carolina, and the St. John's River, Florida. Trawl collections from four nonconsecutive seasons in the period July 1980 to December 1982 indicated that the fish community is dominated by the family Sciaenidae, particularly juvenile forms. Spot (Leiostomus xanthurus) and Atlantic croaker (Micropogonias undulatus) were the two most abundant species and dominated catches during all seasons. Atlantic menhaden (Brevoortin tyrannus) was also very abundant, but only seasonally (winter and spring) dominant in the catches. Elasmobranch fIShes, especially rajiforms and carcharinids, contributed to much of the biomass of fishes collected. Total fish abundance was greatest in winter and lowest in summer and was influenced by the seasonality of Atlantic menhaden and Atlantic croaker in the catches. Biomass was highest in spring and lowest in summer, and was influenced by biomass of spot. Fish density ranged from 321 individuals and 12.2 kg per hectare to 746 individuals and 25.2 kg per hectare. Most species ranged widely throughout the bight, and showed some evidence of seasonal migration. Species assemblages were dominated by ubiquitous year-round residents of the coastal waters of the bight. Diversity (H') was highest in summer, and appeared influenced by the evenness of distribution of individuals among species. (PDF file contains 56 pages.)

Index numbers and productivity measurement in multispecies fisheries: an application to the Pacific Coast Trawl Fleet

This study is concerned with the measurement of total factor prodnctivity in the marine fishing industries in general and in the Pacific coast trawl fishery in particular. The study is divided into two parts. Part I contains suitable empirical and introductory theoretical material for the examination of productivity in the Pacific coast trawl Deet. It is self-contained, and contains the basic formulae, empirical results, and discussion. Because the economic theory of index numbers and productivity is constantly evolving and is widely scattered throughout the economics literature, Part D draws together the theoretical literature into one place to allow ready access for readers interested in more details. The major methodological focus of the study is upon the type of economic index number that is most appropriate for use by economists with the National Marine Fisheries Service. This study recommends that the following types of economic index numbers be used: chain rather than fIxed base; bilateral rather than multilateral; one of the class of superlative indices, such as the Tornqvist or Fisher Ideal. (PDF file contains 40 pages.)