Life history and fisheries ecology of weakfish, Cynoscion regalis, in the Chesapeake Bay region

Otoliths, scales, dorsal spines, and pectoral fin rays were compared to determine the best hardpart for ageing weakfish, Cynoscion regalis. Sectioned otoliths showed the clearest marks and were validated by the marginal increment method for ages 1-5. Traditionally-used scales were found to be less-precise and to underage older fish. Most weakfish from the Chesapeake Bay region were 200-600 mm TL and ages 1-4. Weakfish were not fully-recruited to commercial foodfish grades until age 2. Maximum observed age was 17 from a Delaware Bay fish collected in 1985. Current maximum observed ages were age 12 in Chesapeake Bay and age 11 in Delaware Bay. Fish older than age 6 were rare in both areas. Weakfish growth was well-described by the von Bertalanffy growth model (R&\sp2& = 0.98, N = 857). There was no evidence Delaware Bay weakfish reached a larger asymptotic length or size-at-age than Chesapeake Bay fish. However, maximum size and age from both areas has fluctuated in the past thirty years. Maximum size greatly increased from the late 1960\u27s until roughly 1985, as did the numbers of large fish, apparently due to a series of strong year-classes, beginning in the late 1960\u27s. Weakfish are multiple spawners with indeterminate fecundity and a spawning season from May to August, in the Chesapeake Bay region. Sex ratios were approximately 3:1, females to males, in 1990-1992. Mean length at first maturity for males and females was 164 and 170 mm TL, respectively. Most fish were mature by age one and all fish were mature by age 2. Spawning activity was not consistent throughout the spawning season or between 1991 and 1992. Batch fecundities ranged from 75,289-517,845 eggs/female and significantly increased with both TL and somatic weight. Spawning frequency was every 2-3 days in 1991 and every 12-13 days in 1992, leading to an average annual fecundity of 7,369,750 eggs/females in 1991 and 1,808,056 eggs/female in 1992. Patterns of spawning activity within and between years appeared closely associated with feeding success. Yield-per-recruit analysis indicated that, over a likely range of natural mortality rates, growth overfishing is currently occurring in the Chesapeake Bay region. Current t&\sb{lcub}\rm c{rcub}& is &\le& age 2, whereas maximum yield consistently occurred at t&\sb{lcub}\rm c{rcub}& &\ge& age 6

A Comparison Of A Validated Otolith Method To Age Weakfish, Cynoscion-Regalis, With The Traditional Scale Method

Otoliths, scales, dorsal spines, and pectoral-fin rays were compared to ascertain the best hardpart for determining the age of weakfish, Cynoscion regalis. Each showed concentric marks, which could be interpreted as annuli. Sectioned otoliths, however, consistently showed the clearest marks, had 100% agreement between and within readers, and were validated by the marginal increment method for ages 1-5. This validated method of ageing weakfish was then compared with the traditionally used scale method. The scale method was less precise, as demonstrated by lower percent agreement, and generally assigned younger ages for fish older than age 6 (as determined by otoliths). Consequently, mean sizes at age based on scales showed no clear signs of an asymptote, whereas those based on otoliths did. Otolith annuli formed in April and May, whereas scale annulus formation was more variable, ranging from April to August. This extended time of annulus formation made scales poorly suited for back calculation

Maturity, Spawning, And Ovarian Cycle Of Atlantic Croaker, Micropogonias-Undulatus, In The Chesapeake Bay And Adjacent Coastal Waters

The reproductive biology of Atlantic croaker, Micropogonias undulatus, collected during 1990-91 from commercial catches in Chesapeake Bay and in Virginia and North Carolina coastal waters (n=3,091), was studied by using macroscopic and microscopic gonad staging, the gonadosomatic index, oocyte diameter distributions, and histological analysis. Atlantic croaker are multiple spawners with asynchronous oocyte development and indeterminate fecundity. Mean length at first maturity for males and females was 182 and 173 mm TL, respectively. More than 85% of both sexes were mature by the end of their first year and all were mature by age 2. Spawning extends over a protracted period (July-December), but individual fish apparently spawn over a shorter interval. Eleven gravid and running-ripe females were collected within the Chesapeake Bay suggesting some spawning occurs in estuarine waters. Monthly sex ratios indicated a strong predominance of females during the main period of spawning. A high incidence of atretic, advanced yolked oocytes in spawning females collected throughout the spawning season suggests that a surplus production of yolked oocytes may be part of the reproductive strategy of Atlantic croaker

Age And Growth Of Weakfish, Cynoscion Regalis, In The Chesapeake Bay-Region With A Discussion Of Historical Changes In Maximum Size

Weakfish, Cynoscion regalis, were collected in 1989-93 from commercial catches in the Chesapeake Bay region, and special collections of large fish were made in Delaware Bay. Ages were based on sectioned otoliths. Most weakfish were 200-600 mm TL and ages 1-4 years. Maximum age was 17 years from a 1985 Delaware Bay fish. Maximum current observed ages were 12 years in Chesapeake Bay and 11 years in Delaware Bay. However, fish older than age 6 were rare in both areas. There was no evidence that Delaware Bay fish reached a larger maximum size or maximum age than Chesapeake Bay fish. Although weakfish size was a poor predictor of age, weakfish growth was well described by the von Bertalanffy growth model (r(2)=0.98, n=854). Maximum size and age has fluctuated in both Chesapeake and Delaware Bays over the past thirty years. In both areas the maximum size of fish, based on citation records, greatly increased from the late 1960\u27s until the mid-1980\u27s, as did the numbers of these large fish. These fluctuations appear to be due to a series of strong year classes, beginning in the late 1960\u27s

Development of Age Determination Methods, Life History/Population Dynamics Information, and Yield-per-Recruit Simulation Modeling to Evaluate the Potential for Growth and Recruitment Overfishing of weakfish, Cynoscion regali, in the Chesapeake Bay

The weakfish, Cynoscion regalis, supports large recreational fisheries in the Chesapeake Bay region, where it has historically shown large fluctuations in abundance. Although many studies have been conducted on this species in this region over the last 50 years or more, directed studies commencing at least as early as Nesbit (1954) and Massmann et al. (1958), little information has existed to support yield modeling and wise management. The present study was undertaken to provide basic life history/population dynamics information and yield modeling needed to wisely manage this species in the Chesapeake Bay region, and to evaluate the role that fishing plays in their fluctuations. Accordingly, the basic objectives of the present study were threefold: 1) To develop validated methods of age determination required to conduct basic life history/population dynamics studies, 2) To develop basic life history/population dynamics information required to conduct yield modeling and to provide a background against which modeling can be interpreted, and 3) To conduct, as feasible, yield-per-recruit and eggsper- recruit modeling needed to evaluate growth overfishing, recruitment potential, and to provide advice for wise management

Reproductive timing in marine fishes: variability, temporal scales, and methods

Reproductive timing can be defined as the temporal pattern of reproduction over a lifetime. Although reproductive timing is highly variable in marine fishes, certain traits are universal, including sexual maturity, undergoing one or more reproductive cycles, participating in one or more spawning events within a reproductive cycle, release of eggs or offspring, aging, and death. These traits commonly occur at four temporal scales: lifetime, annual, intraseasonal, and diel. It has long been known that reproductive timing affects reproductive success, especially in terms of the onset of sexual maturity and the match or mismatch between seasonal spawning and offspring survival. However, a comprehensive understanding of variability in reproductive timing over species, populations, and temporal scales is lacking. In addition, there is a need to assess how variability in reproductive timing affects a population’s resilience. Because natural selection occurs at the individual level, this necessitates an understanding of within-population (i.e., individual) variability in reproductive timing and how fishing may impact it through age truncation and size-specific selectivity or fisheries-induced evolution. In this paper, we review the temporal aspects of reproductive strategies and the four most-studied reproductive timing characteristics in fishes: sexual maturity, spawning seasonality, spawning frequency, and diel periodicity. For each characteristic, we synthesize how it has traditionally been measured, advances in understanding the underlying physiology, its role in equilibriumbased fish population dynamics, and its importance to reproductive success. We then provide a review of emerging methodology—with an emphasis on ovarian histology—to improve our ability to assess variability in reproductive timing both among populations and within populations.We are grateful to Fish Reproduction and Fisheries (European Cooperation in Science and Technology Action FA0601) for funding the Fourth Workshop on Gonadal Histology of Fishes (Cadiz, Spain, 2009) and for funding the lead author’s travelPeer reviewe

Características del rendimiento reproductivo del hermafrodita simultáneo Serranus scriba en el Mediterráneo Occidental (Islas Baleares)

We studied multiple individual parameters that affect the reproductive output in the painted comber Serranus scriba, a simultaneous hermaphroditic fish that is widely exploited by recreational fishing in temperate marine coastal regions. Batch fecundity was significantly affected by maternal size, but was not related to maternal age or condition. However, egg quality as estimated by egg dry weight was significantly influenced by the interaction effect of maternal size and age. An empirical assessment demonstrated the existence of a diel spawning pattern based on a daily release of a partial fraction of eggs related to sunset time. Buoyancy varied during the incubation period, but it consistently resulted in positive buoyancy that situated the eggs near the top of the water column. This study represents the first estimation of reproductive output of the simultaneous hermaphrodites S. scriba and also provides a comprehensive study about the potential maternal factors that affect egg production. These results are a crucial step towards ongoing efforts to improve the stock assessment of this species.Se estudiaron varios parámetros individuales que afectan el éxito reproductivo de la especie Serranus scriba, un pez hermafrodita simultáneo que es intensamente explotado por la pesca recreativa en regiones costeras de aguas templadas. La fecundidad parcial está significativamente relacionada con el tamaño de los individuos; pero no se encontró relación con la edad o condición. Sin embargo, la calidad de los huevos (estimada a partir del peso seco) resultó significativamente influenciada por la interacción del tamaño y edad de los individuos. Se demostró empíricamente la existencia de un patrón de desove diario, basado en la puesta diaria de una fracción de los huevos del total con anterioridad a la puesta del sol. La flotabilidad de los huevos varió durante el período de incubación; pero presentando de forma consistente una flotabilidad positiva que sitúa a los huevos liberados cerca de la parte más superficial de la columna de agua. Este estudio representa la primera estimación de los parámetros reproductivos relacionados con la producción de huevos en el hermafrodita simultáneo Serranus scriba. Proporciona además un detallado estudio sobre los posibles factores parentales que afectan a la producción de huevos en esta especie. Estos resultados son un paso fundamental para los esfuerzos en curso para mejorar la evaluación y gestión de las poblaciones de Serranus scriba

Emerging issues and methodological advances in fisheries reproductive biology

Although incorporating detailed reproductive data into all stock assessments is not a practical goal, the need to understand how reproductive biology affects population productivity is being increasingly recognized. More research focused on reproductive biology—coupled with a shift towards a resilience perspective in fisheries science—is resulting in challenges to many long-held assumptions; the emergence of important new issues; and identification of the need to improve data and methods used in reproductive studies. Typically, data for reproductive studies are based on an assessment of gonadal development, which is most accurately evaluated with histology. This special section of Marine and Coastal Fisheries contains contributions from a workshop on the gonadal histology of fishes that was held in Cadiz, Spain, during June 2009. These papers cover a wide range of species and reproductive topics while introducing improved and new histological techniques. In this introduction, we address the following needs: (1) to employ standardization, thereby improving our ability to conduct comparative studies; (2) to better understand patterns of gonadal development and spawning events over time; and (3) to move beyond the spawning stock biomass paradigm. We identify the contributions of special section papers to these topics and conclude by suggesting needsThis workshop was jointly sponsored by FRESH (COST Action FA0601; www.fresh-cost.org) and the AFS Marine Fisheries Section.Peer reviewe