The coarse fishes of Britain

The need for research upon the coarse fishes of Britain, questions of the breeding and rearing of large numbers of young fish, more especially roach, was established back in 1937. The investigation which was begun in 1939 at Barrington in Cambridgeshire was therefore, with the full approval of the National Federation of Anglers, devoted to the general life histories of as many species as possible. Now, five years later, the results of the investigation are presented in the hope that they will provide a basis of knowledge upon which sound policies can be devised for the improvement of fish stocks and the increase of sport. In this report the scientific data, which will be published in full elsewhere, have been condensed as much as possible, but nothing of importance has been omitted and nothing has been concealed.

Reprodução de peixes de riachos: uma abordagem comparativa entre as estratégias r e K

No presente trabalho, objetivou-se caracterizar a estratégia reprodutiva, enfatizando o investimento energético, de duas espécies de peixe do rio Ubatiba, Maricá, Rio de Janeiro: Parotocinclus maculicauda (K-estrategista) e Astyanax hastatus (r-estrategista). Foram realizadas coletas bimestrais de Junho de 2010 a Abril de 2011 totalizando 236 exemplares amostrados de A. hastatus e 234 de P. maculicauda. Para cada exemplar foram registrados os dados de comprimento padrão (Cp, cm), peso total (Pt, g), peso gonadal (Pg, g), sexo e estádio de maturação. Através da estrutura de tamanho, observamos que as fêmeas atingem maior comprimento, em relação aos machos, para as duas espécies. A relação peso/ comprimento evidenciou para ambas as espécies, crescimento alométrico negativo (inferior a 3), demonstrando crescimento mais longelíneo. Para a proporção sexual, o teste χ2 foi aplicado e indicou que, para as duas espécies, há significativamente mais fêmeas. A distribuição sexual no ano mostrou que as fêmeas se mantêm em maioria durante todo o ano para P. maculicauda. Para A. hastatus este padrão também se mantém, porém com exceção do bimestre Novembro/Dezembro, quando o número de machos torna-se um pouco maior. O tamanho de primeira maturação mostrou-se o mesmo para ambas as espécies (2,5 a 3,0 cm). A variação temporal da freqüência de indivíduos reprodutivos e não reprodutivos juntamente com a distribuição temporal dos valores individuais de IGS mostrou que P. maculicauda se reproduz com maior intensidade nas estações chuvosas (Setembro a Abril), reduzindo sua atividade reprodutiva de maneira significativa nas estações secas (Maio a Agosto). Já A. hastatus demonstrou regular atividade reprodutiva durante todo o ano com pequeno pico no bimestre Novembro/ Dezembro. Desova do tipo total foi registrada para Astyanax, enquanto que para Parotocinclus registrou-se desova parcelada em três lotes. Em ambas as espécies foi observada relação inversa entre volume e a quantidade de ovócitos produzidos, com A. hastatus produzindo muitos ovócitos (fecundidade: 463 + 213 ovócitos/grama de peixe) de reduzido volume (diâmetro = 800 μm e volume = 0,26 mm3) e P. maculicauda produzindo número bem inferior (fecundidade: 47 + 13 ovócitos/grama de peixe), porém com volume superior (diâmetro = 1.600 μm e volume = 2,14 mm3). Com isso o valor energético relativo também se mostrou superior, com A. hastaus produzindo ovócitos vitelogênicos com 0,4+ 0,08 cal/unidade e P. maculicauda produzindo os mesmos ovócitos com 1,8+ 1,1 cal/unidade. Para a produção energética total investida na produção de gametas, foi considerado o tipo de desova de cada espécie, com Astyanax investindo 50,5 + 24 calorias/grama/grama de peixe e Parotocinclus investindo 88,4 + 72,46 cal/grama/grama de peixe, porém sem diferenças significativas (Mann-Whitney; U =235,0, p=0,08), indicando, portanto que independente da estratégia adotada (r ou K), o gasto energético na produção de ovócitos é a mesma.

Reproduction de Ethmalosa fimbriata (Bowdich) en lagune Aby (Côte d'Ivoire)

Ethmalosa fimbriata (Bowdich) is the most abundant clupeid in the Ivorian artisanal fisheries. It represents over 60% of lagoon catches. In Aby lagoon the size at first sexual maturity is situated at 9.6 cm for male and 9.9 cm for female. The reproduction takes place twice a year during the high salinity periods from February to May and July to August. This reproduction does not affect significantly the sex-ratio, the mean of which varies from 35% to 36%, depending the period. The fecondity is very fluctuating and varies from 11000 eggs to 148000 eggs per female.

Reproduction et fécondité du machoiron Chrysichthys nigrodigitatus en élevage

Different rearing facilities (concrete tanks, pens and ponds) were tested for suitability as spawning environments. The concrete tanks and the pens in the lagoon gave the best results as to the number of spawns obtained. Of the three types of spawning devices tested, containers with a 150 mm opening at one of the two ends were preferably used by the fish. The brooders in the spawning facilities spontaneously entered the spawning containers to deposit their eggs without external human intervention. Actual fecundity estimates ranged from 9805 to 40597.

Biologie de Ethmalosa Fimbriata (Bowdich) en Côte d'Ivoire. 3 - Étude des Migrations en Lagune Ebrié

Spawning of bonga (Ethmalosa fimbriata Bowdich) takes place in polyhalin waters (Sppt. > 5ppt.). Migrations of young fish were studied by the mean of length data observed in different points of the lagoon from the artisanal fishery. Bonga remain 4 months in the hatchery (6 cm), before they expand in the whole lagoon until the age of 9/10 months. After this expansion phase, the fishes come back to the spawning fields (spawning length: 14/15 cm). Postspawning fishes leave the lagoon. Between birth and spawning, bonga are not affected by salinity changes, but reproduction occurs only in waters where salinity is higher than 5ppt.

A note on the von Bertalanffy growth function concerning the allocation of surplus energy to reproduction

We propose an extended form of the von Bertalanffy growth function (VBGF), where the allocation of surplus energy to reproduction is considered. Any function can be used in our model to describe the ratio of energy allocation for reproduction to that for somatic growth. As an example, two models for energy allocation were derived: a step-function and a logistic function. The extended model can jointly describe growth in adult and juvenile stages. The change in growth rate between the two stages can be either gradual or steep; the latter gives a biphasic VBGF. The results of curve fitting indicated that a consideration of reproductive energy is meaningful for model extension. By controlling parameter values, our comprehensive model gives various growth curve shapes ranging from indeterminate to determinate growth. An increase in the number of parameters is unavoidable in practical applications of this new model. Additional information on reproduction will improve the reliability of model estimates.

Distributions and abundances of Pacific sardine (Sardinops sagax) and other pelagic fishes in the California Current Ecosystem during spring 2006, 2008, and 2010, estimated from acoustic–trawl surveys

The abundances and distributions of coastal pelagic fish species in the California Current Ecosystem from San Diego to southern Vancouver Island, were estimated from combined acoustic and trawl surveys conducted in the spring of 2006, 2008, and 2010. Pacific sardine (Sardinops sagax), jack mackerel (Trachurus symmetricus), and Pacific mackerel (Scomber japonicus) were the dominant coastal pelagic fish species, in that order. Northern anchovy (Engraulis mordax) and Pacific herring (Clupea pallasii) were sampled only sporadically and therefore estimates for these species were unreliable. The estimates of sardine biomass compared well with those of the annual assessments and confirmed a declining trajectory of the “northern stock” since 2006. During the sampling period, the biomass of jack mackerel was stable or increasing, and that of Pacific mackerel was low and variable. The uncertainties in these estimates are mostly the result of spatial patchiness which increased from sardine to mackerels to anchovy and herring. Future surveys of coastal pelagic fish species in the California Current Ecosystem should benefit from adaptive sampling based on modeled habitat; increased echosounder and trawl sampling, particularly for the most patchy and nearshore species; and directed-trawl sampling for improved species identification and estimations of their acoustic target stren

Distribution patterns of tidepool fishes on a tropical flat reef

Rockpools on a tropical f lat reef off the southeastern coast of Brazil were sampled to determine the influence of pool morphometry and water characteristics on fish community structure. The pool closest to the inner fringe of the reef had lower salinity and higher temperature due to inflow of groundwater. The other pools varied only with respect to their morphometric characteristics, algal cover, and bottom composition. Species with a strong affinity for estuarine- like waters characterized the pool closest to the beach and distinguished its fish community from that of the other pools. Instead of being strongly structured by the physicochemical setting and position in the reef, fish communities of the other pools were determined by behavioral preferences and intra- and interspecific interactions. Differences in community structure were related to pool size (the larger sizes permitting the permanency of schooling species), to algal cover (which allowed camouflage for large predatory species), to bottom composition (which provided substrate for turf flora available to territorial herbivores), and to ecological effects (e.g., competition, territoriality, and predation). Although distribution patterns of tidepool fishes have previously been related to the availability of niches, independent of pool position in the reef, our results show synergistic interactions between water properties, presence or absence of niches, and ecological relationships in structuring tidepool fish communities.

Day and night abundance, distribution, and activity patterns of demersal fishes on Heceta Bank, Oregon

Most shallow-dwelling tropical marine fishes exhibit different activity patterns during the day and night but show similar transition behavior among habitat sites despite the dissimilar assemblages of the species. However, changes in species abundance, distribution, and activity patterns have only rarely been examined in temperate deepwater habitats during the day and night, where day-to-night differences in light intensity are extremely slight. Direct-observation surveys were conducted over several depths and habitat types on Heceta Bank, the largest rocky bank off the Oregon coast. Day and night fish community composition, relative density, and activity levels were compared by using videotape footage from a remotely operated vehicle (ROV) operated along paired transects. Habitat-specific abundance and activity were determined for 31 taxa or groups. General patterns observed were similar to shallow temperate day and night studies, with an overall increase in the abundance and activity of fishes during the day than at night, particularly in shallower cobble, boulder, and rock ridge habitats. Smaller schooling rockfishes (Sebastes spp.) were more abundant and active in day than in night transects, and sharpchin (S. zacentrus) and harlequin (S. variegatus) rockfish were significantly more abundant in night transects. Most taxa, however, did not exhibit distinct diurnal or nocturnal activity patterns. Rosethorn rockfish (S. helvomaculatus) and hagfishes (Eptatretus spp.) showed the clearest diurnal and nocturnal activity patterns, respectively. Because day and night distributions and activity patterns in demersal fishes are likely to influence both catchability and observability in bottom trawl and direct-count in situ surveys, the patterns observed in the current study should be considered for survey design and interpretation.

Biomass and reproduction of Pacific sardine (Sardinops sagax) off the Pacific northwestern United States, 2003–2005

The Pacific sardine (Sardinops sagax) is distributed along the west coast of North America from Baja California to British Columbia. This article presents estimates of biomass, spawning biomass, and related biological parameters based on four trawl-ichthyoplankton surveys conducted during July 2003 –March 2005 off Oregon and Washington. The trawl-based biomass estimates, serving as relative abundance, were 198,600 t (coefficient of variation [CV] = 0.51) in July 2003, 20,100 t (0.8) in March 2004, 77,900 t (0.34) in July 2004, and 30,100 t (0.72) in March 2005 over an area close to 200,000 km2. The biomass estimates, high in July and low in March, are a strong indication of migration in and out of this area. Sardine spawn in July off the Pacific Northwest (PNW) coast and none of the sampled fish had spawned in March. The estimated spawning biomass for July 2003 and July 2004 was 39,184 t (0.57) and 84,120 t (0.93), respectively. The average active female sardine in the PNW spawned every 20–40 days compared to every 6–8 days off California. The spawning habitat was located in the southeastern area off the PNW coast, a shift from the northwest area off the PNW coast in the 1990s. Egg production in off the PNW for 2003–04 was lower than that off California and that in the 1990s. Because the biomass of Pacific sardine off the PNW appears to be supported heavily by migratory fish from California, the sustainability of the local PNW population relies on the stability of the population off California, and on local oceanographic conditions for local residence.

Increases in the relative abundance of mid-trophic level fishes concurrent with declines in apex predators in the subtropical North Pacific, 1996–2006

Catch rates for the 13 most abundant species caught in the deep-set Hawaii-based longline fishery over the past decade (1996–2006) provide evidence of a change among the top North Pacific subtropical predators. Catch rates for apex predators such as blue shark (Prionace glauca), bigeye (Thunnus obesus) and albacore (Thunnus alalunga) tunas, shortbill spearfish (Tetrapturus angustirostris), and striped marlin (Tetrapturus audax) declined by 3% to 9% per year and catch rates for four midtrophic species, mahimahi (Coryphaena hippurus), sickle pomfret (Taractichthys steindachneri), escolar (Lepidocybium flavobrunneum), and snake mackerel (Gempylus serpens), increased by 6% to 18% per year. The mean trophic level of the catch for these 13 species declined 5%, from 3.85 to 3.66. A shift in the ecosystem to an increase in midtrophic-level, fast-growing and short-lived species is indicated by the decline in apex predators in the catch (from 70% to 40%) and the increase in species with production to biomass values of 1.0 or larger in the catch (from 20% to 40%). This altered ecosystem may exhibit more temporal variation in response to climate variability.

Use of pop-up satellite archival tag technology to study postrelease survival of and habitat use by estuarine and coastal fishes: an application to striped bass (Morone saxatilis)

Pop-up satellite archival tags (PSATs) have been used to study movements, habitat use, and postrelease survival of large pelagic vertebrates, but the size of these tags has historically precluded their use on smaller coastal species. To evaluate a new generation of smaller PSATs for the study of postrelease survival and habitat use of coastal species, we attached Microwave Telemetry, Inc., X-tags to ten striped bass (Morone saxatilis) 94–112 cm total length (TL) caught on J hooks and circle hooks during the winter recreational fishery in Virginia. Tags collected temperature and depth information every five minutes and detached from the fish after 30 days. Nine of the ten tags released on schedule and eight transmitted 30% to 96% (mean 78.6%) of the archived data. Three tags were physically recovered during or after the transmission period, allowing retrieval of all archived data. All eight striped bass whose tags transmitted data survived for 30 days after release, including two fish that were hooked deeply with J hooks. The eight fish spent more than 90% of their time at depths less than 10 m and in temperatures of 6–9°C, demonstrated no significant diel differences in depth or temperature utilization (P>0.05), and exhibited weak periodicities in vertical movements consistent with daily and tidal cycles.