Diel differences in catches of Western Baltic Spring Spawning Herring Larvae (Clupea harengus)

Comparative night and day catches of herring larvae were taken during the Rügen-Herring-Larval-Survey (RHLS) in 2007 and 2008 in the Greifswalder Bodden which is the main spawning area of the Western Baltic Spring Spawning Herring. The quantities and the size composition of larvae caught during night and day were examined. During night more larvae were caught compared to the samples taken at daytime, especially with larvae larger than 25 mm. This indicates avoidance reactions, which increase with the developmental stage of the larvae. The differences of the night and day catches are relatively constant until a length of about 25 mm, thus the night/day effect does not influence estimations concerning larvae smaller than 25 mm (e.g. N20 index). There might be an impact on estimations for larger larvae due to the night/day effect. For further research other aspects like cloud coverage at night, phase of the moon, underwater visibility and turbidity should be taken into account. These aspects might influence the avoidance reactions.

Fischlarven der westlichen Ostsee – Biodiversitätsuntersuchungen von 2000 bis 2005

Fish larvae surveys provide information on the species composition in an area of investigation and leads to a better understanding of the entire fish community. Since 2000 every year in April/May an ichthyoplankton survey in ICES-Subdivision 22 and 24 has been performed to sample the plankton community in the western Baltic Sea. One objective was to acquire indicators of possible changes in the natural structures of the fish community. The time series derived from the Bongo-Net samples is too short to show a trend in larval densities. Up to now samples in the western Baltic Sea yielded only low mean densities. According to the reproductive biology the fish species were divided in three major groups: -Fish species with a long developmental phase in the plankton community -Small short living species with benthic eggs and a reduced planktonic phase -Guests without local spawning populations Species were identified, which were absent in the plankton of the western Baltic Sea in the 1960s and 1970s.

On the physical and biological oceanography near the entrance of the Gulf of California, October 1966-August 1967

ENGLISH: A study of the temporal and spatial distribution of larval tunas and the concomitant oceanic conditions was made in cooperation with the Direccion General de Pesca e Industrias Conexas of Mexico. Field work consisted of eight hydrographic cruises made from October 1966 through August 1967 near the entrance of the Gulf of California. From January through April, surface currents were southerly at velocities up to 20 cm/sec; currents in June were variable in direction and mostly less than 10 cm/sec; by August the surface current was northerly at 10-15 cm/sec. Surface winds were usually secondary to the distribution of mass as an influence on the surface circulation. Currents at 100 m were generally similar in direction to those at the surface, but the water moved more slowly. Between the surface and 100 m, southbound currents crossed the entrance of the Gulf at velocities of 5-10 cm/sec during January and April, forming frontal boundaries with the California Current water, which often occurred south of the entrance. From April to August, the median concentration of surface chlorophyll a increased from 0.65 to 0.97 mg/m3, while the median productivity increased from 5.6 mgC/m3/day in April to 17.8 mgC/m3/day in June before returning to 2.6 mgC/m3/day in August. Primary productivity was closely correlated with the concentration of surface chlorophyll a. Productivity was generally higher in the vicinity of the Gulf than that found for water in the open Pacific. Productivity was highest near Islas Las Tres Marias and second highest near Cabo San Lucas, both locations of local upwelling. The standing crop of phytoplankton was shown to be subjected to progressively heavier grazing pressure in the spring and summer by zooplankton. SPANISH: Un estudio de la distribución temporal y espacial de las larvas de atún y de las condiciones oceánicas concomitantes fue realizado en cooperación con la Dirección General de Pesca e Industrias Conexas de México. El trabajo experimental consistió en ocho cruceros hidrográficos realizados desde octubre 1966 hasta agosto 1967, cerca a la entrada del Golfo de California. De enero a abril, las corrientes superficiales fueron meridionales alcanzando velocidades hasta de 20 cm/seg; las corrientes en junio fueron variables en dirección y la mayoría con una velocidad de menos de 10 cm/seg; en agosto la corriente superficial fue septentrional a 10-15 cm/seg, Los vientos superficiales fueron por lo común secundarios a la dístríbucíón de la masa, como una influencia de la circulación superficial. Las corrientes a 100 m fueron generalmente similares en dirección a las de la superficie, pero el agua se movió más lentamente. Entre la superficie y los 100 m, las corrientes que se dirigen hacia el sur cruzaron la entrada del Golfo a velocidades de 5-10 cm/seg durante enero y abril formando límites frontales con el agua de la Corriente de California, que apareció a menudo al sur de la entrada. De abril a agosto, la concentración media de la clorofila a superficial aumentó de 0.65 a 0.97 mg/m3, mientras que la productividad mediana aumentó de 5.6 mgC/m3/día en abril hasta 17.8 mgC/m3/día en junio antes de regresar a 2.6 mgC/m3/día en agosto. La productividad primaria se correlacionó estrechamente con la concentración de clorofila a superficial. La productividad fue generalmente más alta en la vecindad del Golfo que aquella encontrada en el agua de alta mar del Pacífico. La productividad fue más alta cerca a las Islas Tres Marías, y el segundo máximo fue cerca al Cabo San Lucas, ambas localidades de afloramiento local. Se indicó que la reserva permanente de fitoplancton estaba sujeta por el zooplancton a una fuerta presión progresiva de apacentamiento en la primavera y el verano. (PDF contains 116 pages.)

Fischarten der westlichen Ostsee – Untersuchungen von 2000 bis 2002

Ichthyoplankton provides information on the species com-position in an area of investigation and leads to a better understanding of the entire fish community. Every year since 1993 May/June (from 2000 in April/May) an ichthyoplankton survey in ICES Subdivision 22 and 24 has been done to sample the plankton community in the western Baltic Sea. One objective was to acquire indicators of possible changes in the natural structures of the fish com-munity. The time series derived from the Bongo-Net samples is too short to show a trend in larval densities. Up to now samples in the western Baltic Sea yielded only low mean densities. According to the reproductive biology the fish species were divided in three major groups: •Fish species with a long developmental phase in the plankton community •Small short lived species with benthic eggs and a reduced planktonic phase •Guests without local spawning populations. Species were identified, which were absent in the plankton of the western Baltic Sea in the 1960s and 1970s.

Das M74-Syndrom des Ostseelachses (Salmo salar): Symptome, Verbreitung und Ursachen

An overview is presented on the M74-Syndrome of Baltic salmon which is known since 1974 and which, since 1992, has caused considerable losses of artificially produced yolk-sac larvae in Swedish and Finnish hatcheries responsible for compensatory salmon stocking programmes. The syndrome only affects offspring of wild salmon ascending the rivers for spawning and not offspring derived from salmon broodstocks permanently kept in hatcheries. The syndrome seems to be restricted to the Baltic Sea where it has been recorded in all of the remaining Swedish (except the west coast) and Finnish salmon rivers as well as in populations of Estonian rivers and the Russian River Neva. In Sweden and in Finland, the syndrome has been recorded in recent years in offspring of up to 80 % of female salmon used for spawning and resulted in a larval mortality of up to 90 %. A nutrition-associated thiamine (vitamin B1) deficiency is considered as primary cause. However, other environmental factors seem to be involved in addition. There is concern that the syndrome constitutes a major threat with respect to the survival of the few still naturally reproducing populations of Baltic salmon.

Ichthyoplanktonaufnahmen als Beitrag zu Biodiversitätsuntersuchungen in der westlichen Ostsee

Ichthyoplankton material provides information on the species composition in an area of investigation and leads to a better understanding of the entire fish community. Since 1993 every year in May and/or June an ichthyoplankton survey in ICES-Subdivision 22 and 24 has been performed to sample the plankton community of fishery resources in the western Baltic Sea. One objective was to get signs of possible changes in the natural structures of this fish community. The time series derived from the Bongo-Net samples does not show a clear trend in larval densities. Values varied, but up to now samplings in the western Baltic Sea yielded only low mean densities. According to the kind of reproductive biology the fish species were divided in three major groups: • Fish species with a long developmental phase in the plankton community • Small short living species with benthic eggs and a reduced plankton phase • Guests without local spawning populations. Species could be identified, which were absent in the fish larvae catches of the western Baltic Sea in the 60s and 70s.

A review of the crayfish fishery of Nigeria with special reference to the Cross River State

The fishery for crayfish is of considerable importance in the maritime region of the Cross River State, Nigeria, where it forms an important occupation of a host of fishermen. Crayfish landings from this State contributed 11% to the national marine fish landings within the period 1980 to 1984 and also in the same period the volume of crayfish alone formed 26% of the marine fish landings within the State. The species exploited as crayfish include Palaemon hastatus; Hippolysmata hastatoides, and Macrobrachium sp; mixed with the larval, and juveniles of pink shrimp Panaeus dourarum. They are generally small in size ranging from 7 cm (maximum) to 2.5 cm. Crayfish are caught all year round along the Niger Delta, but particularly along the river estuaries and littoral waters of the Cross River State with the highest production occurring in March to May. Crayfish are usually smoked, and occasionally sun-dried, and they form an indispensable food item in the diet of the people of the entire southern States in particular and Nigeria in general. It appears that crayfish landings could be substantially increased without depleting the stock, if a proper exploratory survey is undertaken of the Niger delta, and the Cross River estuaries to chart potentially rich grounds of this resource

Effects of human chorionic gonadotropin (HCG), toad and Clarias pituitary hormogenates on spawning in the catfish: Clarias Lazera (C. and V.) and Clarias anguillaris (Linne)

Experiment on induced spawning of Clarias lazera and C. anguillaris using human chorionic gonadotropin (HCG) freshly prepared toad and Clarias pituitary hormogenates were carried out. Clarias pituitary hormogenates induced spawning in C. lazera and C. anguillaris at dosage levels of 0.27-0.46 mg/150 g body weight or 2 glands/fish of equivalent weights. HCG induced spawning in C. anguillaris at 500 i.u/500 g body weight but failed in C. lazera. Toad pituitary was not successful at even a higher dosage level of 0.60 mg/150 g body weight. The implications of these results are discussed. Spawning occurred in the HCG (and Clarias pituitary treated females in less than 12 hours after injection and subsequent examination of ovaries of the spawned fish showed incomplete spawning. Furthermore, fertilization occurred, following spawning in the piscine pituitary hormone treated male and female fish but failed in the HCG (treated pair. A mean fertilization rate of 50-90% was recorded. Possible explanations of these observations are advanced. The hatching time of 24-48 hours and a mean hatching rate of 75-90% were recorded. A high larval mortality of up to 95% was observed in the post yolk-sac stag after 8 days. The need for the development of appropriate larval food for Clarias species in culture practice is stressed

Seltene Fischlarven in den Ichthyoplanktonfängen der westlichen Ostsee im Zeitraum 1993 - 1996

Distribution and abundance of fish eggs and larvae in North Sea and Baltic Sea have been objectives of fishery research for over 100 years. Most fish species produce pelagic eggs or larvae. The early developmental stages of many marine fish species important to commercial fishery are part of plankton communities, and can be sampled by a single gear. Collections of fish in their larval phase provide material for studies of many aspects of fishery research: e.g. information on plankton communities and abundance of fish species in the area of investigation.

Physical circulation measurements in Pamlico Sound, used to locate new oyster sanctuaries

The population of eastern oyster, C. virginica, has declined over the last century on most areas of the east and gulf coasts. North Carolina’s restoration efforts depend on the construction of subtidal oyster reefs to be used as broodstock sanctuaries in Pamlico Sound, NC. Successful restoration of the oyster population requires several thriving reefs connected as a meta-population. C. virginica has a 2-3 week larval stage, during which it gradually settles through the water column. Larvae that can travel from one reef to another during that stage form the basis of a meta-population. (PDF contains 3 pages)

Habitat enhancing marine structures: Creating habitat in urban waters

Although maritime regions support a large portion of the world’s human population, their value as habitat for other species is overlooked. Urban structures that are built in the marine environment are not designed or managed for the habitat they provide, and are built without considering the communities of marine organisms that could colonize them (Clynick et al., 2008). However, the urban waterfront may be capable of supporting a significant proportion of regional aquatic biodiversity (Duffy-Anderson et al., 2003). While urban shorelines will never return to their original condition, some scientists think that the habitat quality of urban waterfronts could be significantly improved through further research and some design modifications, and that many opportunities exist to make these modifications (Russel et al., 1983, Goff, 2008). Habitat enhancing marine structures (or HEMS) are a potentially promising approach to address the impact of cities on marine organisms including habitat fragmentation and degradation. HEMS are a type of habitat improvement project that are ecologically engineered to improve the habitat quality of urban marine structures such as bulkheads and docks for marine organisms. More specifically, HEMS attempt to improve or enhance the physical habitat that organisms depend on for survival in the inter- and sub-tidal waterfronts of densely populated areas. HEMS projects are targeted at areas where human-made structures cannot be significantly altered or removed. While these techniques can be used in suburban or rural areas restoration or removal is preferred in these settings, and HEMS are resorted to only if removal of the human-made structure is not an option. Recent research supports the use of HEMS projects. Researchers have examined the communities found on urban structures including docks, bulkheads, and breakwaters. Complete community shifts have been observed where the natural shoreline was sandy, silty, or muddy. There is also evidence of declines in community composition, ecosystem functioning, and increases in non-native species abundances in assemblages on urban marine structures. Researchers have identified two key differences between these substrates including the slope (seawalls are vertical; rocky shores contain multiple slopes) and microhabitat availability (seawalls have very little; rocky shores contain many different types). In response, researchers have suggested designing and building seawalls with gentler slopes or a combination of horizontal and vertical surfaces. Researchers have also suggested incorporating microhabitat, including cavities designed to retain water during low tide, crevices, and other analogous features (Chapman, 2003; Moreira et al., 2006) (PDF contains 4 pages)

The effects of Moina artificial diet and nutrase xyla supplemented artificial diet on growth and survival of Clarias gariepinus larvae

An experiment was carried out to investigate the effects of Moina, artificial diet (55% CP) and nutrase xyla supplemented artificial diet on growth performances and survival rates of Clarias gariepinus larvae. A combination of Moina and artificial diet (with or without nutrass xyla) resulted in higher growth performance and survival rates during a 12-day nursing time with specific growth rates of 30.04-32.15% d super(-1) and survival rates of 87.5-90%. Best growth performance and survival rate was obtained with a combination of Moina and artificial diet supplemented with nutrias xylem. Feeding of Moina and artificial diet supplemented, with nutrias xyla alone to the larval led to a lower growth performance of 25.60-27.04% d super(-1). However, the survival rate of Monia of larvae fed a combination of Moina and artificial diet (with or without nutrias xylem supplementation) artificial diet without nutrias xylem addition proved relatively less suitable for larval rearing of Clarias gariepinus owing to a low survival rate of 69% and growth performance of 19.7% d super(-1). This study showed the feasibility of feeding a combination of Moina and nutrias xylem supplemented artificial diet to the larvae of Clarias gariepinus

Aquaculture potentials and investment opportunity in shrimps and prawns farming in Nigeria

Some aspects of the aquaculture potentials and investment opportunity in shrimps and prawn farming in Nigeria were overviewed. This paper presents the breeding pattern, spawner availability, culture water-type and properties, feeds and feeding regimes and other factors needed in practical shrimps and prawns culture. The culture systems, water management, larval management, stocking density, feeding strategies and diseases were fully discussed. The investment opportunity available as government plans to boost production of these resources from both artisanal and aquaculture sector was documented. Management strategies needed in practical practices of shrimps and prawns culture were enlisted. Effected efforts from the government were listed in this paper

Botanical insecticides prescription for fish pest control and infestation free protein yield

The dry powders of four local species namely Piper guineense Schum and Thonn, Aframomum melegueta Schum, Zingiber officinale Rose; Capsicum annum Miller at three concentrations of 15g, 20g and 25g.kg were evaluated for their insecticidal effects against the larval of the dried fish weevil Demestes maculates Degeer. All the four species showed some effectiveness with P. guineense given a 100% mortality at the end of 72 hours at the three concentrations. The other species though gave less mortality were able to slow down the rate of development of the larvae to the adult size

Zur Verbreitung der einzelnen Altersklassen des Köhlers, Pollachius virens (L.), in der nördlichen Nordsee (ICES-Div. IV a)

The distribution was studied by analysing the catches during four research vessel cruises in summer and eight cruises in winter in the period 1985 - 1993. The emmigration of young saithe, spending the larval and first juvenil stages in the inshore waters of Norway and Scotland, starts during the summer in an age of two years.