Biological reference points for managing kingfish, Scomberomorus commerson, in Oman

The 1987-1995 length composition of quarterly catches of Scomberomorus commerson (Lacepede 1800) was analyzed to determine various biological reference points for management purposes. These include: fishing mortality producing maximum yield-per-recruit in weight (F sub(max)), fishing mortality producing 50% relative mean mature biomass (F sub(50)), and fishing mortality producing recruits that would exactly replace their parent stock (F sub(rep)). F sub(max) provided misleading suggestions to increase fishing mortality on the stock which is currently at a low level. On the other hand, both F sub(50) and F sub(rep) provided acceptable results, suggesting reduction on the current fishing mortality by 17-40%.

Biological parameters, body length-weight and length-height relationships for various species in Greek waters

Biological/fisheries parameters (L sub(oo) M, F) are presented for four fish species (Gadiculus argenteus; Gaidropsarus mediterraneous; Symphurus ligulatus; Lepidorhombus boscii) as well as body length-weight and length-height relationships for 11 and 12 fish species, respectively, estimated from trawl samples collected using three different cod-ends (stretched mesh size: 14 mm and 20 mm diamond-shaped and 20 mm square-shaped) during 1993-1994, in the western Aegean and North Euboikos Gulf, Greece. The fisheries paramaters, estimated from length-frequency using the ELEFAN approach and software, are discussed in the light of recent information on the selectivity of the presently used trawl cod-end (14 mm diamond shaped)

Variability in spawning frequency and reproductive development of the narrow-barred Spanish mackerel (Scomberomorus commerson) along the west coast of Australia

The narrow-barred Spanish mackerel (Scomberomorus commerson) is widespread throughout the Indo-West Pacific region. This study describes the reproductive biology of S. commerson along the west coast of Australia, where it is targeted for food consumption and sports fishing. Development of testes occurred at a smaller body size than for ovaries, and more than 90% of males were sexually mature by the minimum legal length of 900 mm TL compared to 50% of females. Females dominated overall catches although sex ratios within daily catches vary considerably and females were rarely caught when spaw n ing. Scomberomorus commerson are seasonally abundant in coastal waters and most of the commercial catch is taken prior to the reproductive season. Spawning occurs between about August and November in the Kimberley region and between October and January in the Pilbara region. No spawning activity was recorded in the more southerly West Coast region, and only in the north Kimberley region were large numbers of fish with spawning gonads collected. Catches dropped to a minimum when spawning began in the Pilbara region, when fish became less abundant in inshore waters and inclement weather conditions limited fishing on still productive offshore reefs. Final maturation and ovulation of oocytes took place within a 24-hour period, and females spawned in the afternoon-evening every three days. A third of these spawning females released batches of eggs on consecutive days. Relationships between length, weight, and batch fecundity are presented.

Maximum likelihood estimation of mortality and growth with individual variability from multiple length-frequency data

We consider estimation of mortality rates and growth parameters from length-frequency data of a fish stock and derive the underlying length distribution of the population and the catch when there is individual variability in the von Bertalanffy growth parameter L∞. The model is flexible enough to accommodate 1) any recruitment pattern as a function of both time and length, 2) length-specific selectivity, and 3) varying fishing effort over time. The maximum likelihood method gives consistent estimates, provided the underlying distribution for individual variation in growth is correctly specified. Simulation results indicate that our method is reasonably robust to violations in the assumptions. The method is applied to tiger prawn data (Penaeus semisulcatus) to obtain estimates of natural and fishing mortality.

Freshwater Biological Association 1929-1979. The first fifty years

Booklet telling the story of the FBA from its founding in 1929 until its Golden Jubilee in 1979. The booklet aimed to produce a readable account of those aspects of freshwater biology that have been among the main themes of the Association's research, as well as some aspects of its history and the philosophy guiding its foundation. The publication includes many images of the FBA's work and history as well as images and illustrations on lake ecology and applied science.

Variabilidade espacial e temporal das concentrações de clorofila na Baía de Guanabara (RJ) utilizando imagens MERIS e dados in situ

Este trabalho teve como objetivo principal implementar um algoritmo empírico para o monitoramento do processo de eutrofização da Baía de Guanabara (BG), Rio de Janeiro (RJ), utilizando dados de clorofila-a coletados in situ e imagens de satélite coletadas pelo sensor MERIS, a bordo do satélite ENVISAT, da Agência Espacial Européia (ESA). Para a elaboração do algoritmo foi utilizada uma série histórica de clorofila-a (Out/2002 a Jan/2012) fornecida pelo Laboratório de Biologia Marinha da UFRJ, que, acoplada aos dados radiométricos coletados pelo sensor MERIS em datas concomitantes com as coletas in situ de clorofila-a, permitiu a determinação das curvas de regressão que deram origem aos algorítmos. Diversas combinações de bandas foram utilizadas, com ênfase nos comprimentos de onda do verde, vermelho e infra-vermelho próximo. O algoritmo escolhido (R = 0,66 e MRE = 77,5%) fez uso dos comprimentos de onda entre o verde e o vermelho (665, 680, 560 e 620 nm) e apresentou resultado satisfatório, apesar das limitações devido à complexidade da área de estudo e problemas no algoritmo de correção atmosférica . Algorítmos típicos de água do Caso I (OC3 e OC4) também foram testados, assim como os algoritmos FLH e MCI, aconselhados para águas com concentrações elevadas de Chl-a, todos com resultados insatisfatório. Como observado por estudos pretéritos, a Baia de Guanabara possui alta variabilidade espacial e temporal de concentrações de clorofila-a, com as maiores concentrações no período úmido (meses: 01, 02, 03, 10, 11 12) e nas porções marginais (~ 100 mg.m-3), particularmente na borda Oeste da baia, e menores concentrações no período seco e no canal principal de circulação (~ 20 mg.m-3). O presente trabalho é pioneiro na construção e aplicação de algoritmos bio-óptico para a região da BG utilizando imagens MERIS. Apesar dos bons resultados, o presente algorítmo não deve ser considerado definitivo, e recomenda-se para trabalhos futuros testar os diferentes modelos de correção atmosférico para as imagens MERIS.

History of the Atlantic Pearl-Oyster, Pinctata imbricata, Industry in Venezuela and Colombia, with Biological and Ecological Observations

In the 1500’s, the waters of Venezuela and to a lesser extent Colombia produced more natural pearls than any place ever produced in the world in any succeeding century. Atlantic pearl-oysters, Pinctata imbricata Röding 1798, were harvested almost entirely by divers. The pearls from them were exported to Spain and other European countries. By the end of the 1500’s, the pearl oysters had become much scarcer, and little harvesting took place during the 1600’s and 1700’s. Harvesting began to accelerate slowly in the mid 1800’s and has since continued but at a much lower rate than in the 1500’s. The harvesting methods have been hand collecting by divers until the early 1960’s, dredging from the 1500’s to the present, and hardhat diving from 1912 to the early 1960’s. Since the mid 1900’s, Japan and other countries of the western Pacific rim have inundated world markets with cultured pearls that are of better quality and are cheaper than natural pearls, and the marketing of natural pearls has nearly ended. The pearl oyster fishery in Colombia ended in the 1940’s, but it has continued in Venezuela with the fishermen selling the meats to support themselves; previously most meats had been discarded. A small quantity of pearls is now taken, and the fishery, which comprised about 3,000 fishermen in 1947, comprised about 300 in 2002.

Reef Habitats in the Middle Atlantic Bight: Abundance, Distribution, Associated Biological Communities, and Fishery Resource Use

One particular habitat type in the Middle Atlantic Bight is not well recognized among fishery scientists and managers, although it is will known and used by recreational and commercial fisheries. This habitat consists of a variety of hard-surface, elevated relief "reef" or reef-like environments that are widely distributed across the predominantly flat or undulating, sandy areas of the Bight and include both natural rocky areas and man-made structures, e.g. shipwrecks and artificial reefs. Although there are natural rock and shellfish reefs in southern New England coastal waters and estuaries throughout the Bight, most reef habitats in the region appear to be man-made reef habitat modification/creation may be increasing. Very little effort has been devoted to the study of this habitat's distribution, abundance, use by living marine resources and associated biological communities (except on estuarine oyster reefs) and fishery value or management. This poorly studied and surveyed habitat can provide fish refuge from trawls and can be a factor in studies of the distribution and abundance of a variety of reef-associated fishery resources. This review provides a preliminary summary of information found on relative distribution and abundance of reef habitat in the Bight, the living marine resources and biological communities that commonly use it, threats to this habitat and its biological resources, and the value or potential value of artificial reefs to fishery or habitat and its biological resources, and the value or potential value of artificial reefs to fishery or habitat managers. The purpose of the review is to initiate an awareness among resource managers about this habitat, its role in resource management, and the need for research.

Biological Characteristics and Fishery Assessment of Alaska Plaice, Pleuronectes quadrituberculatus, in the Eastern Bering Sea

Alaska plaice, Pleuronectes quadrituberculatus, is one of the major flatfishes in the eastern Bering Sea ecosystem and is most highly concentrated in the shallow continental shelf of the eastern Bering Sea. Annual commercial catches have ranged from less than 1,000 metric tons (t) in 1963 to 62,000 t in 1988. Alaska plaice is a relatively large flatfish averaging about 32 cm in length and 390 g in weight in commercial catches. They are distributed from nearshore waters to a depth of about 100 m in the eastern Bering Sea during summer, but move to deeper continental shelf waters in winter to escape sea ice and cold water temperatures. Being a long-lived species (>30 years), they have a relatively low natural mortality rate estimated at 0.20. Maturing at about age 7, Alaska plaice spawn from April through June on hard sandy substrates of the shelf region, primarily around the 100 m isobath. Prey items primarily include polychaetes and other marine worms. In comparison with other flatfish, Alaska plaice and rock sole, Pleuronectes bilineatus, have similar diets but different habitat preferences with separate areas of peak population density which may minimize interspecific competition. Yellowfin sole, Pleuronectes asper, while sharing similar habitat, differs from these two species because of the variety of prey items in its diet. Competition for food resources among the three species appears to be low. The resource has experienced light exploitation since 1963 and is currently in good condition. Based on the results of demersal trawl surveys and age-structured analyses, the exploitable biomass increased from 1971 through the mid-1980’s before decreasing to the 1997 level of 500,000 t. The recommended 1998 harvest level, Allowable Biological Catch, was calculated from the Baranov catch equation based on the FMSY harvest level and the projected 1997 biomass, resulting in a commercial harvest of 69,000 t, or about 16% of the estimated exploitable biomass.

Yellowfin Sole, Pleuronectes asper, of the Eastern Bering Sea: Biological Characteristics, History of Exploitation, and Management

Yellowfin sole, Pleuronectes asper, is the second most abundant flatfish in the North Pacific Ocean and is most highly concentrated in the eastern Bering Sea. It has been a target species in the eastern Bering Sea since the mid-1950's, initially by foreign distant-water fisheries but more recently by U.S. fisheries. Annual commercial catches since 1959 have ranged from 42,000 to 554,000 metric tons (t). Yellowfin sole is a relatively small flatfish averaging about 26 cm in length and 200 g in weight in commercial catches. It is distributed from nearshore waters to depths of about 100 m in the eastern Bering Sea in summer, but moves to deeper water in winter to escape sea ice. Yellowfin sole is a benthopelagic feeder. It is a longlived species (>20 years) with a correspondingly low natural mortality rate estimated at 0.12. After being overexploited during the early years of the fishery and suffering a substantial decline in stock abundance, the resource has recovered and is currently in excellent condition. The biomass during the 1980's may have been as high as, if not higher than, that at the beginning of the fishery. Based on results of demersal trawl surveys and two age structured models, the current exploitable biomass has been estimated to range between 1.9 and 2.6 million t. Appropriate harvest strategies were investigated under a range of possible recruitment levels. The recommended harvest level was calculated by multiplying the yield derived from the FOI harvest level (161 g at F = 0.14) hy an average recruitment value resulting in a commercial harvest of 276,900 t, or about 14% of the estimated exploitable biomass.

Biological Analysis of Two Management Options for the Atlantic Menhaden Fishery

Biological implications of two managment options (the closed corridor and the recommended shortened season (Option 7) options) for the Atlantic menhaden, Brevoortia tyrannus, fishery are reported based on purse-seine landings and port sampling data from 1970 to 1984 and captain's daily fishing reports from 1978 to 1982. Large catches of age-O menhaden raise concern for growth overfishing. Area-specific yield-per-recruit analyses are used to investigate the biological consequences of these management options. The closed corridor option indicates coastwide gains in yield-per-recruit ranging from 0.3 to 7.2% depending on changes in fishing activity with most areas showing gains. The shortened fishing season indicates coastwide gains in yield per recruit ranging from O. 4 to 10.2% depending onf ishing year with most geographic areas showing gains. The shortened fishing season option offers the greatest gains when large numbers ofy oung menhaden would be caught late in the fishing year, while gains from the closed corridor option depend on how the fishing fleet responds to that management plan. The shortened season offers greater potential coastwide gains to the fishery, but also may result in greater losses to the North Carolina fall fishery. The analytical approach is applicable to the management of other coastal migratory fish stocks that fall under the Atlantic States Marine Fisheries Commission or other interstate management groups.

Ecologia funcional de duas comunidades de peixes de riacho: a importância da variação intraespecífica e interespecífica em diferentes atributos ecológicos

A compreensão sobre a estrutura e funcionamento das comunidades biológicas é uma das principais questões das teorias ecológicas e principalmente no contexto de diversidade funcional, já que os atributos das espécies influenciam fortemente a distribuição e o papel que os organismos desempenham nos ecossistemas. Neste trabalho, tivemos como objetivo avaliar a variabilidade intraespecífica e interespecífica dos atributos ecológicos em duas assembleias de peixes localizadas em riachos sujeitos a diferentes condições físicas. A variação na utilização dos recursos, seja entre indivíduos e/ou entre espécies pode nos ajudar a compreender as interações bióticas e a estrutura das populações e comunidades de peixes. Os atributos referentes a morfologia, dieta, uso do habitat e alguns aspectos comportamentais foram avaliados e suas variações foram testadas a partir dos valores individuais. As coletas foram realizadas em dois riachos tropicais, sendo um localizado no ambiente da Mata Atlântica e o outro, no ambiente do semiárido brasileiro. Além das análises empíricas, uma revisão bibliográfica sobre o tema e uma possível composição funcional dos grupos de peixes de riacho foram descritas no capítulo 1 da presente tese. Nos capítulos 2 e 3, foram testadas as hipóteses de que existe alta variabilidade intraespecífica em relação aos atributos ecológicos dos peixes e que esta variabilidade é influenciada pela alta disponibilidade de recursos, enquanto no capítulo 4, a variação entre os indivíduos foi testada em relação a aspectos comportamentais. Nossos resultados revelaram que, de fato, a variação intraespecífica foi alta em ambas as assembleias, porém na assembleia do semiárido, esta variabilidade foi maior. Este resultado pode estar relacionado a alta disponibilidade de recursos espaciais encontrada nesta localidade. A morfologia e a dieta apresentaram correlação significativa, porém foi fraca em ambas as assembleias, demonstrando assim a importância de mensurar esses dois aspectos da biodiversidade dos peixes. Os resultados relacionados ao uso do habitat também apresentaram alta variabilidade entre os indivíduos e entre as espécies nos dois riachos em estudo. A assembleia do semiárido apresentou maior variabilidade física com potenciais microambientes formados por bancos de macrófitas a serem explorados pelos organismos, permitindo assim, o uso diferenciado e a escolha individual por diferentes recursos espaciais. A variabilidade individual também foi encontrada no comportamento social de duas espécies desta assembleia, onde houve formação de cardumes compostos por indivíduos maiores nas extremidades com maior capacidade de fuga na relação presa-predador. Neste sentido, a alta variação intraespecífica para diversos aspectos funcionais avaliados neste trabalho evidencia ainda mais a importância de mensurar as características ecológicas dos peixes a partir de valores individuais. Adicionalmente, a partir desta ferramenta, podemos compreender melhor a complementaridade da especialização e originalidade ecológica dos indivíduos e finalmente, sugerir de que forma os atributos funcionais dos organismos influenciam a estrutura das populações e comunidades de peixes de riachos tropicais