Effect of sampling interval on estimates of larval supply

Estimates of larval supply can provide information on year-class strength that is useful for fisheries management. However, larval supply is difficult to monitor because long-term, high-frequency sampling is needed. The purpose of this study was to subsample an 11-year record of daily larval supply of blue crab (Callinectes sapidus) to determine the effect of sampling interval on variability in estimates of supply. The coefficient of variation in estimates of supply varied by 0.39 among years at a 2-day sampling interval and 0.84 at a 7-day sampling interval. For 8 of the 11 years, there was a significant correlation between mean daily larval supply and lagged fishery catch per trip (coefficient of correlation [r]=0.88). When these 8 years were subsampled, a 2-day sampling interval yielded a significant correlation with fishery data only 64.5% of the time and a 3-day sampling interval never yielded a significant correlation. Therefore, high-frequency sampling (daily or every other day) may be needed to characterize interannual variability in larval supply.

Size and year class composition of catch, age and growth of yellowfin tuna in the Eastern Tropical Pacific Ocean for the years 1954-1958

ENGLISH: Data on the size composition of catch for the years 1954-1958 have been studied to determine year class composition, age and growth of yellowfin tuna in the Eastern Tropical Pacific Ocean. Direct age determination of tropical tunas has not yet proven reliable; however, this analysis has shown that the length-frequency distributions themselves are adequate to determine year class structure and growth rates. Absolute age has been estimated by comparing the average time of spawning with the time at which age groups initially appear in the catch. SPANISH: Los datos sobre la composición del tamaño de la pesca durante los años 1954-1958 han sido estudiados con el objeto de determinar la composición de las clases anuales, la edad y el crecimiento del atún aleta amarilla en el Océano Pacífico Oriental Tropical. Las determinaciones directas de la edad de los atunes tropicales no han probado todavía ser de confianza; sin embargo, este análisis ha demostrado que las distribuciones de la frecuencia de las longitudes son adecuadas para determinar la estructura de las clases anuales y de las tasas de crecimiento. La edad absoluta ha sido estimada mediante la comparación de la época promedio de desove con la epoca en que los grupos de edades comienzan a aparecer en la pesca.

Year class mortality, abundance and yield-per-recruit of yellowfin tuna in the eastern Pacific Ocean, 1954-1959

ENGLISH: One primary duty of the Inter-American Tropical Tuna Commission is to estimate the maximum sustainable catches of yellowfin tuna (Neothunnus macropterus) and skipjack (Katsuwonus pelamis), and to investigate and recommend proposals to maintain the stocks at levels which will permit these catches to be obtained. To do this, there is required some means of predicting yields relative to fishing intensity. . . The age composition of catch, and growth rate of yellowfin tuna for recent years have now been estimated (Hennemuth, 1961). In this paper, relative abundance at age of yellowfin tuna shall be estimated -and used, in turn, to estimate total mortality rate. Yield-per-recruit calculations, based on Beverton and Holt's (1957) simple equation, will be presented to compare present utilization with theoretical maxima under varying levels of fishing mortality and different ages at first capture. SPANISH: Uno de los principales deberes de la Comisión Interamericana del Atún Tropical es estimar las pescas máximas sostenibles de los atunes aleta amarilla (Neothunnus macropterus) y barrilete (Katsuwonus pelamis) , así como estudiar y recomendar proposiciones para mantener los stocks a niveles que permitan obtener estas pescas. Para lograr este propósito se requieren algunos medios que permitan predecir el rendimiento en relación con la intensidad de la pesca. . La composición de edades de la pesca y la tasa de crecimiento del atún aleta amarilla en años recientes han sido estimadas ahora (Hennemuth, 1961). En este trabajo, la abundancia relativa a una edad dada de esta especie será estimada y usada, a su vez, para estimar la tasa de mortalidad total. Los cálculos del rendimiento por recluta, basados en la ecuación simple de Beverton y Holt (1957), serán presentados para comparar la utilización actual con los máximos teóricos bajo valores variables de mortalidad por la pesca y a diferentes edades a la primera captura.

Size and year class composition of catch, age and growth of yellowfin tuna in the Eastern Tropical Pacific Ocean, 1951-1961

ENGLISH: Analysis of yellowfin tuna size-composition data encompassing data for purse-seiners and baitboats, and including data collected prior to the Commission's sampling program, has permitted a more careful examination of variations in growth rates of yellowfin year classes. SPANISH: El análisis de los datos de la composición de tamaños del atún aleta amarilla correspondiente a los que provienen de los barcos rederos y de carnada, e incluyendo datos recolectados previamente al programa de muestreo de la Comisión, ha permitido un examen más cuidadoso de las variaciones en las tasas de crecimiento de las clases anuales del atún aleta amarilla.

Estimation of year class abundance and mortality of yellowfin tuna in the Eastern Tropical Pacific

ENGLISH: Age composition of catch, and growth rate, of yellowfin tuna have been estimated by Hennemuth (1961a) and Davidoff (1963). The relative abundance and instantaneous total mortality rate of yellowfin tuna during 1954-1959 have been estimated by Hennenmuth (1961b). It is now possible to extend this work, because more data are available; these include data for 1951-1954, which were previously not available, and data for 1960-1962, which were collected subsequent to Hennemuth's (1961b) publication. In that publication, Hennemuth estimated the total instantaneous mortality rate (Z) during the entire time period a year class is present in the fishery following full recruitment. However, this method may lead to biased estimates of abundance, and hence mortality rates, because of both seasonal migrations into or out of specific fishing areas and possible seasonal differences in availability or vulnerability of the fish to the fishing gear. Schaefer, Chatwin and Broadhead (1961) and Joseph etl al. (1964) have indicated that seasonal migrations of yellowfin occur. A method of estimating mortality rates which is not biased by seasonal movements would be of value in computations of population dynamics. The method of analysis outlined and used in the present paper may obviate this bias by comparing the abundance of an individual yellowfin year class, following its period of maximum abundance, in an individual area during a specific quarter of the year with its abundance in the same area one year later. The method was suggested by Gulland (1955) and used by Chapman, Holt and Allen (1963) in assessing Antarctic whale stocks. This method, and the results of its use with data for yellowfin caught in the eastern tropical Pacific from 1951-1962 are described in this paper. SPANISH: La composición de edad de la captura, y la tasa de crecimiento del atún aleta amarilla, han sido estimadas por Hennemuth (1961a) y Davidoff (1963). Hennemuth (1961b), estimó la abundancia relativa y la tasa de mortalidad total instantánea del atún aleta amarilla durante 1954-1959. Se puede ampliar ahora, este trabajo, porque se dispone de más datos; éstos incluyen datos de 1951 1954, de los cuales no se disponía antes, y datos de 1960-1962 que fueron recolectados después de la publicación de Hennemuth (1961b). En esa obra, Hennemuth estimó la tasa de mortalidad total instantánea (Z) durante todo el período de tiempo en el cual una clase anual está presente en la pesquería, consecutiva al reclutamiento total. Sin embargo, este método puede conducir a estimaciones con bias (inclinación viciada) de abundancia, y de aquí las tasas de mortalidad, debidas tanto a migraciones estacionales dentro o fuera de las áreas determinadas de pesca, como a posibles diferencias estacionales en la disponibilidad y vulnerabilidad de los peces al equipo de pesca. Schaefer, Chatwin y Broadhead (1961) y Joseph et al. (1964) han indicado que ocurren migraciones estacionales de atún aleta amarilla. Un método para estimar las tasas de mortalidad el cual no tuviera bias debido a los movimientos estacionales, sería de valor en los cómputos de la dinámica de las poblaciones. El método de análisis delineado y usado en el presente estudio puede evitar este bias al comparar la abundancia de una clase anual individual de atún aleta amarilla, subsecuente a su período de abundancia máxima en un área individual, durante un trimestre específico del año, con su abundancia en la misma área un año más tarde. Este método fue sugerido por Gulland (1955) y empleado por Chapman, Holt y Allen (1963) en la declaración de los stocks de la ballena antártica. Este método y los resultados de su uso, en combinación con los datos del atún aleta amarilla capturado en el Pacífico oriental tropical desde 1951-1962, son descritos en este estudio.

Variations in year-class strength and estimates of the catchability coefficient of yellowfin tuna, Thunnus albacares, in the Eastern Pacific Ocean

ENGLISH: Year-class composition of catch, virtual population size and yearclass strength were determined from serial samples of size composition of catches and catch records. Murphy's Solution to the catch equation, which is free from the effects caused by changes in fishing pressure, was used to estimate year-class strength, i.e. the total population of fish age 3/4 years. The resultant estimates indicated that the X55, X56, X57, X62 and X63 year classes were above average and the X58, X59, X60, X61 and X64 year classes were below average. The year-class designation refers to the year of actual entry or presumed year of entry into the commercial fishery (at approximately 1 year of age). The strongest and poorest year classes were the X57 and X61 classes, respectively. The ratio of the strongest to the weakest year class was 2.6. This amount of variation is small compared to that found for other species of fish. It was found that the relationship between stock size and yearclass strength is of no value in predicting year-class strength. As a by-product of the analysis, estimates of the catchability coefficients (qN) of the age groups in the fishery were obtained, These estimates were found to vary with age and time. Age-two fish apparently showed the greatest vulnerability to fishing gear, followed by ages three and one, respectively. The average estimate of the catchability coefficient in weight was calculated and found to compare favorably with Schaefer's estimate. The influence of sea-surface water temperature upon year-class strength was investigated to determine whether the latter can be predicted from a knowledge of sea-surface temperatures prevailing during and following spawning. No correlation was evident. SPANISH: La composición de la clase anual en la captura, el tamaño de la población virtual y la fuerza de clase anual, fueron determinados según una serie de muestras de la composición de tamaño de las capturas y de los registros de captura. La Solución de Murphy de la ecuación de captura, que está libre de los efectos causados por los cambios de la presión de pesca, fue usada para estimar la fuerza de la clase anual, i.e. la población total de peces de 3/4 años. Las estimaciones resultantes indican que las clases anuales X55, X56, X57, X62 y X63 fueron superiores al promedio y que las clases anuales X58, X59, X60, X61 y X64 fueron inferiores al promedio. La designación de la clase anual se refiere al año actual de entrada o al año supuesto de entrada en la pesca comercial (aproximadamente a la edad de 1 año). Las clases anuales más fuertes y más pobres fueron la X57 y X61 respectivamente. La razón de la clase anual más fuerte en relación a la más débil fue 2.6. Esta cantidad de variación es pequeña comparada con la encontrada para otras especies de peces. Se encontró que la relación entre en tamaño del stock y la fuerza de la clase anual no tiene valor en predecir la fuerza de la clase anual. Se obtuvieron estimaciones de los coeficientes de capturabilidad (qN) de los grupos de edad en la pesquería como un producto derivado del análisis. Se encontraron que estas estimaciones variaron con la edad y tiempo. Los peces de edad dos aparentemente presentaron la vulnerabilidad más grande en relación al arte pesquero, seguidos por las edades tres y una, respectivamente. La estimación promedio del coeficiente de capturabilidad en peso fue calculada y se encontró que podía compararse favorablemente con la estimación de Schaefer. La influencia de la temperatura del agua superficial del mar sobre la fuerza de la clase anual fue investigada para determinar si se podía predecir esta última según el conocimíento de las temperaturas superficiales del mar prevalecientes durante el desove y después de éste. No hubo correlación evidente. (PDF contains 44 pages.)

Year class strengths of perch and pike in Windermere

The pike (Esox lucius) year classes are more stable than those of the perch (Perca fluviatilis), and have been shown to be closely correlated with temp conditions during the first few months of life. The perch year class strengths have been more variable; for success they require the presence of several positive conditions and the absence of many adverse conditions which could cause failure, a favourable combination of circumstances rarely occurs. The conclusions refer only to Windermere from 1941-1964.

Year-class formation in Pacific herring (Clupea pallasi) estimated from spawning-date distributions of juveniles in San Francisco Bay, California

Inter and intra-annual variation in year-class strength was analyzed for San Francisco Bay Pacific herring (Clupea pallasi) by using otoliths of juveniles. Juvenile herring were collected from March through June in 1999 and 2000 and otoliths from subsamples of these collections were aged by daily otolith increment analysis. The composition of the year classes in 1999 and 2000 were determined by back-calculating the birth date distribution for surviving juvenile herring. In 2000, 729% more juveniles were captured than in 1999, even though an estimated 12% fewer eggs were spawned in 2000. Spawning-date distributions show that survival for the 2000 year class was exceptionally good for a short (approximately 1 month) period of spawning, resulting in a large abundance of juvenile recruits. Analysis of age at size shows that growth rate increased significantly as the spawning season progressed both in 1999 and 2000. However, only in 2000 were the bulk of surviving juveniles a product of the fast growth period. In the two years examined, year-class strength was not predicted by the estimated number of eggs spawned, but rather appeared to depend on survival of eggs or larvae (or both) through the juvenile stage. Fast growth through the larval stage may have little effect on year-class strength if mortality during the egg stage is high and few larvae are available.

Age and length composition of Columbia Basin chinook, sockeye, and coho salmon at Bonneville Dam in 2001

In 2001, representative samples of adult Columbia Basin chinook (Oncorhynchus tshawytscha), sockeye (O. nerka), and coho salmon (O. kisutch) populations at Bonneville Dam were collected. Fish were trapped, anesthetized, sampled for scales and biological data, revived, and then released adult migrating salmonids. Scales were examined to estimate age composition; the results contributed to an ongoing database for age class structure of Columbia Basin salmon populations. Based on scale analysis of chinook salmon, four-year-old fish (from brood year [BY] 1997) comprised 88% of the spring chinook, 67% of the summer chinook, and 42% of the Bright fall chinook salmon population. Five-year-old fish (BY 1996) comprised 9% of the spring chinook, 14% of the summer chinook, and 9% of the fall chinook salmon population. The sockeye salmon population at Bonneville was predominantly four-year-old fish (81%), with 18% returning as five-year-olds in 2001. The coho salmon population was 96% three-year-old fish (Age 1.1). Length analysis of the 2001 returns indicated that chinook salmon with a stream-type life history are larger (mean length) than the chinook salmon with an ocean-type life history. Trends in mean length over the sampling period for returning 2001 chinook salmon were analyzed. Chinook salmon of age classes 0.2 and 1.3 show a significant increase in mean length over time. Age classes 0.1, 0.3, 0.4, 1.1, 1.2, and 1.4 show no significant change over time. A year class regression over the past 12 years of data was used to predict spring, summer, and Bright fall chinook salmon population sizes for 2002. Based on three-year-old returns, the relationship predicts four-year-old returns of 132,600 (± 46,300, 90% predictive interval [PI]) spring chinook and 44,200 (± 11,700, 90% PI) summer chinook salmon for the 2002 runs. Based on four-year-old returns, the relationship predicts five-year-old returns of 87,800 (± 54,500, 90% PI) spring, 33,500 (± 11,500, 90% PI) summer, and 77,100 (± 25,800, 90% PI) Bright fall chinook salmon for the 2002 runs. The 2002 run size predictions should be used with caution; some of these predictions are well beyond the range of previously observed data.

Age and length composition of Columbia Basin chinook, sockeye, and coho salmon at Bonneville Dam in 2000

In 2000, representative samples of adult Columbia Basin chinook (Oncorhynchus tshawytscha), sockeye (O. nerka), and coho salmon (O. kisutch), populations were collected at Bonneville Dam. Fish were trapped, anesthetized, sampled for scales and biological data, allowed to revive, and then released. Scales were examined to estimate age composition and the results contribute to an ongoing database for age class structure of Columbia Basin salmon populations. Based on scale analysis, four-year-old fish (from brood year (BY) 1996) were estimated to comprise 83% of the spring chinook, 31% of the summer chinook, and 32% of the upriver bright fall chinook salmon population. Five-year-old fish (BY 1995) were estimated to comprise 2% of the spring chinook, 26% of the summer chinook, and 40% of the fall chinook salmon population. Three-year-old fish (BY 1997) were estimated to comprise 14% of the spring chinook, 42% of the summer chinook, and 17% of the fall chinook salmon population. Two-year-olds accounted for approximately 11% of the fall chinook population. The sockeye salmon population sampled at Bonneville was predominantly four-year-old fish (95%), and the coho salmon population was 99.9% three-year-old fish (Age 1.1). Length analysis of the 2000 returns indicated that chinook salmon with a stream-type life history are larger (mean length) than the chinook salmon with an ocean-type life history. Trends in mean length over the sampling period were also analysis for returning 2000 chinook salmon. Fish of age classes 0.2, 1.1, 1.2, and 1.3 have a significant increase in mean length over time. Age classes 0.3 and 0.4 have no significant change over time and age 0.1 chinook salmon had a significant decrease in mean length over time. A year class regression over the past 11 years of data was used to predict spring and summer chinook salmon population sizes for 2001. Based on three-year-old returns, the relationship predicts four-year-old returns of 325,000 (± 111,600, 90% Predictive Interval [PI]) spring chinook and 27,800 (± 29,750, 90% PI) summer chinook salmon. Based on four-year-old returns, the relationship predicts five-year-old returns of 54,300 (± 40,600, 90% PI) spring chinook and 11,000 (± 3,250, 90% PI) summer chinook salmon. The 2001 run size predictions used in this report should be used with caution, these predictions are well beyond the range of previously observed data.

Age and length composition of Columbia Basin chinook, sockeye, and coho salmon at Bonneville Dam in 2002

In 2002, representative samples of migrating Columbia Basin chinook (Oncorhynchus tshawytscha), sockeye (O. nerka), and coho salmon (O. kisutch) adult populations were collected at Bonneville Dam. Fish were trapped, anesthetized, sampled for scales and biological data, revived, and then released. Scales were examined to estimate age composition; the results contributed to an ongoing database for age class structure of Columbia Basin salmon populations. Based on scale analysis of chinook salmon, four-year-old fish (from brood year [BY] 1998) comprised 86% of the spring chinook, 51% of the summer chinook, and 51% of the bright fall chinook salmon population. Five-year-old fish (BY 1997) comprised 13% of the spring chinook, 43% of the summer chinook, and 11% of the bright fall chinook salmon population. The sockeye salmon population at Bonneville was predominantly five-year-old fish (55%), with 40% returning as four-year-olds in 2002. For the coho salmon population, 88% of the population was three-year-old fish of age class 1.1, while 12% were age class 1.0. Length analysis of the 2002 returns indicated that chinook salmon with a stream-type life history are larger (mean length) at age than the chinook salmon with an ocean-type life history. Trends in mean length over the sampling period for returning 2002 chinook salmon were analyzed. Chinook salmon of age classes 1.2 and 1.3 show a significant increase in mean length over the duration of the migration. A year class regression over the past 14 years of data was used to predict spring, summer, and bright fall chinook salmon population sizes for 2003. Based on three-year-old returns, the relationship predicts four-year-old returns of 54,200 (± 66,600, 90% predictive interval [PI]) spring chinook, 23,800 (± 19,100, 90% PI) summer, and 169,100 (± 139,500, 90% PI) bright fall chinook salmon for the 2003 runs. Based on four-year-old returns, the relationship predicts five-year-old returns of 36,300 (± 35,400, 90% PI) spring, 63,800 (± 10,300, 90% PI) summer, and 91,100 (± 69,400, 90% PI) bright fall chinook salmon for the 2003 runs. The 2003 run size predictions should be used with caution; some of these predictions are well beyond the range of previously observed data.

The use of agreement measures and latent class models to assess the reliability of classifying thermally marked otoliths

Otolith thermal marking is an efficient method for mass marking hatchery-reared salmon and can be used to estimate the proportion of hatchery fish captured in a mixed-stock fishery. Accuracy of the thermal pattern classification depends on the prominence of the pattern, the methods used to prepare and view the patterns, and the training and experience of the personnel who determine the presence or absence of a particular pattern. Estimating accuracy rates is problematic when no secondary marking is available and no error-free standards exist. Agreement measures, such as kappa (κ), provide a relative measure of the reliability of the determinations when independent readings by two readers are available, but the magnitude of κ can be influenced by the proportion of marked fish. If a third reader is used or if two or more groups of paired readings are examined, latent class models can provide estimates of the error rates of each reader. Applications of κ and latent class models are illustrated by a program providing contribution estimates of hatchery-reared chum and sockeye salmon in Southeast Alaska.

Major histocompatibility complex class I involvement in the rejection of allogeneic erythrocytes in rainbow trout (Oncorhynchus mykiss)

Major histocompatibility complex genes are thought to be involved in allogeneic graft rejection but not many reports are available on their functional analysis in fish. Analysis of available sequences of MHC genes suggests functions in antigen presentation similar to those found in higher vertebrates. In mammals, the MHC class I and class II molecules are major determinants of allogeneic graft rejection due to their polymorphism in conjunction with their antigen presenting function. In fish, MHC class H molecules are found to be involved in rejection of allogeneic scale grafts. The present study was designed to investigate the involvement of MHC class I molecules in allograft rejection. Erythrocytes were collected from donors of rainbow trout expressed different class MHC class I alleles, stained with two dyes, mixed and grafted to the recipients that were of the same sibling group as the donors. The grafts were rejected by allogeneic recipients and the MHC class I linkage group was the major determinant for the rejection.