bluuebunny/crossref_metadata_2025 huggingface dataset:
Age structure, growth and reproduction of Leuciscus pyrenaicus in an intermittent stream in the Guadalquivir river basin, southern Spain
Authors: Fernández‐Delgado C. , Herrera M.
Published: June 2006

The age, growth and reproduction of Leuciscus pyrenaicus (Günther, 1868), an endemic cyprinid from the Iberian Peninsula, was studied from November 1987 to September 1989 in a small seasonal tributary of the Guadalquivir river basin. Maximum fork lengths observed were a 160 mm male with six scale annuli and a 171 mm female aged 7 +. Maximum ages observed were 7 + in males and 8 + in females. There were no significant differences in the annual growth increments between sexes. Seasonal growth period started in March and continued for 5 to 6 months. Mean lengths of 1 + specimens onwards diminished during summer and/or autumn. Males and females matured in their third and fourth year of life respectively. The overall sex ratio (272 males: 310 females) differed significantly from equality. Spawning began in May and ended in July. L. pyrenaicus is a multiple spawner that releases a minimum of two batches of eggs per female each year. Eggs in each batch were similar in both size (egg diameter) and number released. The relationship between fecundity (Fee) and fork length (mm) was represented by the formula: Fec=1.96 10−3 L2.50.
Gut evacuation of walleye pollock larvae in response to feeding conditions
Authors: Canino M. F. , Bailey K. M.
Published: June 2006

Gut residence times of first‐feeding walleye pollock larvae were measured at 6°C in continuous and discontinuous feeding regimes. Larvae fed tagged copepod prey evacuated their guts more quickly in continuous feeding as compared to the discontinuous feeding treatment. The mean gut residence time was estimated to be 5.0 h for larvae feeding continuously. Gut evacuation by larvae fed tagged prey and then isolated without food (discontinuous treatment) was slower and more variable, with an estimated gut residence time exceeding 8.0 h. Field and laboratory observations suggest that the larval fish gut may be modeled as an intermittent plug‐flow reactor (PFR) in response to diel feeding patterns. The cyclical nature of gut dynamics has implications for gut content analyses and the estimation of daily food rations.
Effect of feeding and lack of food on the growth, gross biochemical and fatty acid composition of juvenile catfish
Authors: Zamal H. , Ollevier F.
Published: June 2006

The effect of feeding and starvation on growth, gross body composition and fatty acid composition of body muscle and liver were investigated in juvenile African catfish (Clarias gariepinus). The relative composition of fatty acids was influenced by starvation. In both liver and muscle there were marked relative decreases of 14: 0, 16: 1n9 and 18: 1n9 fatty acids and relative increases of 20: 5n3 and 22: 6n3 when these were compared to the controls. Preference of utilization of fatty acids from liver and body muscle during starvation was highest for 14: 0>16: 1n9>18: 1n9 and conservation highest for 22: 6n3>20: 5n3. The changes of these fatty acids were smaller in muscle than in the liver.
Susceptibility of brown trout toGyrodactylus salaris(Monogenea) under experimental conditions
Authors: Jansen P. A. , Bakke T. A.
Published: June 2006

Brown trout (Salmo trutta) from anadromous River Lierelva, resident Lake Tunhovd, and resident Nordmarka stocks were exposed toGyrodactylus salaris‐infected salmon parr. The brown trout were fed pellets before the experiments, except for one group of the Nordmarka stock which was starved for 19 days before the experiments. The mean number of parasites declined directly and rapidly post infection for all groups of trout. There were no pronounced differences in resistance between the anadromous and the resident stocks.G. salarisinfections tended to persist longer on starved than on fed trout of the Nordmarka stock. The maximum parasite persistence on trout was 50 days, and as parasite numbers increased on some fish parasite reproduction must have occurred on those trout. However, the limited susceptibility and marked innate resistance of trout toG. salarisestablishment, development and reproduction, suggest parasite metapopulations will not survive on this species. Nevertheless, trout may still play a role in the dispersal ofG. salariswithin and between rivers.
Behaviour of the female beaugregory damselfish (Stegastes leucostictus)
Authors: Horne E. A. , Itzkowitz M.
Published: June 2006

Much less is known about the behaviour of female beaugregory damselfish than about males of the species. This study was initiated to determine behavioural patterns and interactions of female beaugregories on the back reef of Discovery Bay Marine Laboratory, North shore of Jamaica. Females fed, patrolled, and chased intruders in a significantly larger area and ate significantly more per 15‐min observation period than did males. Males spent significantly more time patrolling their territories and chased significantly more total intruders than did females. However, this difference in total chases comes from the fact that males chased the bluehead wrasse, an egg predator, significantly more often than did females while all other species of intruder were chased the same by both sexes. The distance that females travelled from their homesite to court was significantly positively correlated to female body length. This increased distance travelled may relate to mate assessment. Female beaugregory damselfish may be able to be more selective in their choice of mate with increased size and distance travelled.
Genetic variation at isozyme loci in blue whiting from the north‐east Atlantic
Authors: Mork J. , Giæver M.
Published: June 2006

Genetic variation in blue whiting Micromesistius poutassou was investigated by starch gel electrophoresis of enzymes in tissue extracts. A total of 130 specimens from the spawning areas west of the British Isles were collected from trawl catches in 1990 (n= 30) and 1992 (n= 100). In 25 tissue enzyme loci screened for genetic variants in the 1990 sample, polymorphisms (0.95 criterion) were found at IDDH‐2*, IDHP‐2* and PGM‐1*, giving a frequency of polymorphic loci of P0.95= 0.12. In pooled samples the average heterozygosity per locus was estimated at He=0.043 and the effective number of alleles per locus at 2.20, 1.45 and 1.53, respectively, for IDDH‐2*, IDHP‐2* and PGM‐1*.
Catecholamine release and interrenal response of brown trout, Salmo trutta, exposed to aluminium in acidic water
Authors: Brown J. Anne , Whitehead Colin
Published: June 2006

Cannulated brown trout, Salmo trutta, were exposed for 36 h to synthetic water with a low calcium content of pH 5 and similar synthetic water dosed with aluminium to raise the filterable A1 from 5 to 290 μg 1−1 over the 36‐h period. There were no significant disturbances of plasma concentrations of glucose, cortisol or catecholamine (adrenaline and noradrenaline) in fish held in water of pH 5. The addition of aluminium to this acidic synthetic water resulted in a generalized endocrine stress response with a four‐fold increase in plasma glucose concentration after 18 h and a significant increase in plasma cortisol concentration from 24 h onwards when filterable A1 exceeded 200 μg 1−1. Plasma catecholamine concentration indicated an adrenergic stress response in aluminium‐exposed brown trout. A transient doubling in noradrenaline after 6 h in A1 was followed by a larger increase in both plasma adrenaline and noradrenaline concentrations in fish surviving the 36‐h exposure to A1.
Ecological implications of Echinorhynchus gadi parasitism of Baltic cod (Gadus morhua)
Authors: Buchmann K.
Published: June 2006

Of 533 Baltic cod (body length 21–93 cm) 530 were infected with Echinorhynchus gadi at infection intensities from 1 to 490 per host. The heavy infection of large cod (normally not feeding on amphipods) may be explained by a transfer of parasites from prey fishes to the predating large cod.
Maturity, oocyte dynamics and fecundity of the roundnose grenadier from the Rockall Trough
Authors: Kelly C. J. , Connolly P. L. , Bracken J. J.
Published: June 2006

The reproductive biology of roundnose grenadier Coryphaenoides rupestris was investigated against a background of increasing commercial exploitation. Samples were taken from surveys carried out in Rockall Trough between 1993 and 1995. An eight‐point maturity scale was developed based on both visual inspection of the ovaries and histological screening. The various stages of development of roundnose grenadier oocytes were described and the relative proportion of oocyte types and their respective size range in each maturity stage were investigated. The dynamic organization of the ovary indicated a determinate maturation cycle in this species. Population spawning appears to be prolonged, extending from July to at least November. However, data were insufficient to clarify individual spawning duration. The potential fecundity of 29 mature fish ranged from 11 083‐55 175 (63‐95 cm total length). The results were very similar to previous values from the North Atlantic. The reproductive strategy of the roundnose grenadier is discussed in the light of the current commercial exploitation of the Species.
The reproduction of anglerfish Lophius piscatorius Linnaeus from the north‐west coast of Scotland
Authors: Afonso‐Dias I. P. , Hislop J. R. G.
Published: June 2006

The reproductive cycle of anglerfish was studied by examining fresh material obtained from commercial landings and research vessel surveys. The general morphology and histology of the gonads are described. This species has unusual gonads. The testes are tubular, and beanshaped in transverse section. The maturation process of the testis is similar to that of most other teleosts. The ovaries are confluent and form a single, flattened tube. During maturation, the width and, in particular, the length of the ovaries increases dramatically. A gelatinous matrix is produced during the maturation process, which contributes to the enormous size and weight of ripe ovaries. Ripe testes can be found throughout the year, whereas ripened ovaries were found only between November and May. Females outnumbered males in length classes greater than 70 cm and no males larger than 90 cm were found. The estimated mean length at maturity (150%) was 73 cm for females and 49 cm for males. Because only the large female anglerfish are capable of spawning, and because virtually all large anglerfish are female, trends in their abundance resulting from commercial exploitation should be monitored with care.
Deep‐water fishes: evolution and adaptation in the earth's largest living spaces*
Authors: Haedrich R. L.
Published: June 2006

Deep‐water habitats form by far the largest ecosystems on the planet. Enough is known about the lives of deep‐water fishes, despite the difficulties inherent in such study, to give a fairly coherent picture of their overall ecology. Inferences based on individual morphology and taxonomic diversity provided the first clues, but series from the various large national deep‐water expeditions have allowed the working out of detailed life histories, food webs, species associations and biogeography. The particular conditions that characterize deep water everywhere have shaped the nature of deep‐water fishes, and probably the most important factor at play has been the logarithmic decline of food energy available with increasing depth. Comparative study of deep‐pelagic, deep‐demersal, and deep‐lake fishes reveals interesting and intriguing differences with respect to the adaptations and probable history of the faunas in each of these habitats. Deep‐water fishes have long been insulated from any significant human impacts, but deep‐water fisheries, species introductions, pollution and other ecosystem tamperings are changing this situation rapidly. Can these remarkable, enduring and well‐adapted species and assemblages withstand the developing onslaught?
Energetic and life‐history patterns of deep‐sea benthic, benthopelagic and seamount‐associated fish
Authors: Koslow J. A.
Published: June 2006

A review of energy use and the life histories of deep‐water demersal fishes suggests that there are two primary groups or guilds; those that live dispersed over the sea floor and those that aggregate in association with topographic features like seamounts. Dispersed deep‐sea fishes typically have a body plan designed for slow cruising or ‘sit and wait’ predation, and are characterized by very low energy stores and metabolic rates. Scaled for body size, the metabolism of these fishes was comparable to that of bathypelagic fishes. On the other hand, aggregatory deep‐water species are characterized by robust morphology and strong locomotory ability to maintain themselves in environments characterized by strong, variable currents. Their flesh has high protein and lipid but low water content. The metabolic rate of orange roughy, an aggregating deep‐water species, was substantially higher than that of dispersed deep‐water fishes and was comparable to that of haddock, a shelf demersal species. However, although the estimated ration of orange roughy was higher than that of dispersed demersal deep‐water species, its growth rate was comparable and its growth efficiency was far lower due to its high metabolic costs. Large deep‐water dispersed fish species are characterized by late maturity and an extended reproductive period, but these characteristics are less pronounced than in deep seamount‐associated species, which may live in excess of 100 years.
Biomass estimation of orange roughy: a summary and evaluation of techniques for measuring stock size of a deep‐water fish species in New Zealand
Authors: Clark M. R.
Published: June 2006

A number of techniques have been employed to measure biomass of orange roughy in New Zealand. Time series of stratified random trawl surveys in a number of areas over periods of 5–10 years have given relative abundance indices, which have been used in stock reduction analyses to estimate true biomass. This has given confident results for the Chatham Rise stock, and surveys have also shown strong trends in other regions. Acoustic surveys have been carried out on three grounds. They can give relative indices of orange roughy abundance in areas of fiat or medium sloping bottom, and have the potential for estimation of absolute biomass from a single survey. Egg production surveys have been employed on two grounds on the east coast of the North Island, where conditions of tight spawning aggregations and steep bottom topography have limited the success of other methods. Both daily fecundity reduction and annual egg production methods have been used. These have given estimates of true biomass from one‐off surveys, although results are imprecise. Both unstandardized and standardized analyses of commercial catch‐per‐unit‐effort data have given relative indices of abundance, which have formed an important part of stock assessment for several fisheries. No single technique used to measure the size of orange roughy stocks has proven ideal or appropriate in all New Zealand situations. All have advantages and disadvantages, depending on the characteristics of the fishing area and fish behaviour. For two areas, a combination of methods have been applied, which has given more confident results than those from a single technique.
Preliminary stock assessment of the Patagonian toothfish longline fishery around the Falkland Islands
Authors: des Clers S. , Nolan C. P. , Baranowski R. , Pompert J.
Published: June 2006

An experimental fishery for Patagonian toothfish Dissostichus eleginoides was opened in Falkland Island waters briefly in 1992 and then from April 1994. One to two longlines per vessel were usually deployed at night, mostly fishing for 12–30 h at depths between 600 and 2000 m. The characteristics of the vessel, gear, fishing activities and the data collection and analyses methods are described. An initial evaluation of the authors' current understanding of toothfish biology and population dynamics in Falkland Island waters is given. A first analysis of toothfish numbers caught in 1994 suggests that these are changing at rates faster than expected from simple demographic processes. Therefore, despite an intensive monitoring of catch and fishing effort of each vessel, it is still not possible to derive reliable estimates for the size of the toothfish population currently exploited around the Falkland Islands. Migration patterns in and out of the fishery need to be understood before a reliable assessment of the fishery can be made. These results, together with current and future lines of research, are discussed in the light of data available from other toothfish fisheries in austral waters.
Bathysauropsis gigas, a deep‐sea aulopiform fish with a peculiar iris process and a pure‐cone retina
Authors: Somiya H. , Yamakawa T. , Okiyama M.
Published: June 2006

The eyes of the benthic deep‐sea fish Bathysauropsis gigas were examined macroscopically and histologically. A peculiar iris process was found in each eye of the fish. Photoreceptors in the retina were exclusively cones. These cones were all morphologically twin cones, and rods were not observed. The function of these specific characters remains unknown. The retinal structure of Chlorophthalmus albatrossis was described briefly for comparison. The entirely pure‐twin‐cone retina of Bathysauropsis gigas suggest a close relationship with the Chlorophthalmus.
VISION AND SENSORY PHYSIOLOGY The lateral line systems of three deep‐sea fish
Authors: Marshall N. J.
Published: June 2006

The distribution and ultrastructure of the lateral line systems in three taxonomically dispersed deep‐sea fish are described: Poromitra capito, Melanonus zugmayeri and Phrynichthys wedli. They are meso‐ to bathpelagic and are thought to feed on small crustaceans and fish. All possess highly developed lateral line systems, a feature associated with life in the deep sea. Poromitra capito and M. zugmayeri exhibit widened head canals which are connected to the outside by large pores and which contain around 60 large neuromasts. Each neuromast consists of a cupula, shield‐shaped mantle and a sensory plate containing hundreds to thousands of hair cells. Direction of sensitivity is in the long axis of the canal (perpendicular to the long axis of the mantle). Depending on their position on the sensory plate, the hair cells have different morphologies. They fall into three basic classes which, from comparison with past work, may be tuned to different frequencies. Alternatively, the various hair cell morphologies could be interpreted as being members of a developmental or growth sequence. Phrynichthys wedli has no canal organs, these being replaced secondarily by many superficial neuromasts placed on prominent papillae in rows which cover much of the ‘head’ and body. Direction of sensitivity is along the axis of the neuromast row. An extreme proliferation of superficial neuromasts are also found on the heads of P. capito and M. zugmayeri and these are of a type not described before. They consist of stitches, raised on papillae in M. zugmayeri and several mm long in P. capito, in which continuous lines of hair cells, two to three cells wide, are embedded. Direction of sensitivity is perpendicular to the long axis of the stitch. Based on the structure and direction of sensitivity, possible functional implications of all the neuromast types described are compared and discussed.
Greater silver smelt, Argentina silus in Icelandic waters
Authors: Magnússon J. V.
Published: June 2006

This paper presents results obtained from data on the greater silver smelt Argentina silus in Icelandic waters collected by the Marine Research Institute, Iceland, mainly since 1981. The greater silver smelt is most abundant in the waters off the south‐east coast of Iceland clockwise to those off the west coast, but the species has also been observed off the north coast. Differences in the size composition in relation to area and depth are described. The preferred depth range of the greater silver smelt was found to be 300‐600 m and the preferred temperature was about 6°C. Ageing is described showing a relatively fast growth up to the age of 8‐9 years. The age/length and length/weight relations are given. Females grow faster than males. The 50% maturity point is reached by males at a length of 36‐37 cm and at an age of approximately 8 years, and by females at a length of 37‐38 cm and approximately 9 years. Spawning takes place to some extent year round but with one or two periods of greater intensity. Results from experimental fishing are described and problems in connection with a Commercial fishery are discussed.
A preliminary study of two species of flatfish (family: Bothidae) from the south‐west Atlantic
Authors: Yau C. , George M. J. A. , Coggan R. A. , Criado‐Delgado J. A.
Published: June 2006

Two species of the family Bothidae (lefteye flounders), Mancopsetta maculata metadata and M. milfordi occur in the south‐west Atlantic but are caught rarely by commercial bottom trawlers. Little is therefore known about their general biology from this area. A total of 251 M. maculata and 276 M. milfordi were sampled during deep‐water exploratory fishing conducted in November 1994 within the Falkland Islands Interim and Outer Conservation Zones, at depths of 400‐1000 m, using standard commercial bottom trawling gear. The two species were found to have similar geographical distributions between 48.30′‐53.30'S and 55°‐62° W and were often obtained at the same stations in depths of 400‐900 m on the continental slope. Mancopsetta maculata maculata showed a uni‐modal cohort structure with a modal length at the 29‐cm total length size‐class. Males of M. m. maculata outnumbered females in a ratio of 3.5 : 1. Mancopsetta milfordi showed a tri‐modal length distribution, the main mode at the 37‐cm total length size‐class, with females outnumbering males in a ratio of 1.1 : 1. Length‐weight relationships and length‐at‐age information are presented for the two species. Diet was determined from the analysis of stomach contents and, although the major prey type for both species consisted of crustaceans, the morid fish Austrophycis marginata also formed an important part of the diet of M. milfordi. Key words: Mancopsetta maculata maculata; Mancopsetta milfordi; distribution; south‐west Atlantic; size; diet.
Patterns and trends in larval‐stage growth and mortality of teleost fish*
Authors: Houde E. D.
Published: June 2006

Weight‐specific growth (G) and instantaneous mortality (M) rates are linked processes during early life, and the MIG ratio determines stage‐specific mortality. A comparative analysis of five species identified patterns and trends in larval M and G, and their relationship to variability in larval cohort abundance. M declined with respect to body size in all species, although levels of M were variable between taxa and years. Rates of decline in M with respect to size generally were higher than predicted by size‐spectrum theory. G varied between species and years, but was less variable than M. In some species (e.g. striped bass and American shad) G increased appreciably before declining, while in others G declined throughout the larval stage. Consequently, stage‐specific mortality, which is governed by MIG and body size, declined slowly or was relatively constant throughout the larval stage. Cohort biomass declined during the early larval stages. and began to increase only when larvae attained the ‘transition size’ at which MIG < 1.0. Annual variability in transition sizes and ages, which is a consequence of trends, patterns, and variability in MIG, can act to control recruitment. Mortality is growth‐dependent and growth‐related factors are correlated with recruitment potentials, but measures of larval growth alone are not sufficient to predict or explain variability in recruitments.
Larval distribution, abundance, and stock structure of British Columbia herring
Authors: Hay D. E. , McCarter P. B.
Published: June 2006

Pacific herring Clupea pallasi spawn in shallow and intertidal areas. Larval distributions and abundance of three major and several minor stocks were examined to determine if larvae mix among different spawning locations. The surveys were short, intensive, and occurred mainly within the first 30 days of larval life. Each major stock had a discrete larval distribution with continuous larval distributions within stock boundaries. Some overlap of distributions occurred among smaller stocks. Most larvae were found in inshore waters but there were no obvious oceanographic factors, such as fronts or eddies, to explain all the distributions. Estuarine circulation in inlets could promote larval retention in some areas. The results support the present geographic definitions for local herring stocks. The results are generally consistent with the concept of discrete larval distribution, including retention areas, as the basis for herring Stock Structure.
The influence of phase of the moon and physical processes on the input of presettlement fishes to coral reefs
Authors: Kingsford M. , Finn M.
Published: June 2006

At One Tree Island, Great Barrier Reef, Australia, large numbers of reef fish, of sizes that were considered potential settlers, were caught in ichthyoplankton nets that were tethered on the reef crest at night. Comparisons were made, among lunar phases, with wind direction and strength, rate of water flow over the reef crest (facilitated by tide and wind) and changes in local water masses. Analyses for total reef fish and separately, the Gobiidae, Blenniidae, Lutjanidae, Apogonidae, Pomacentridae, Mullidae, Labridae and Scaridae, all showed considerable variation in abundance with time, but peaks in abundance were not concurrent for most families of fish. Differences in temporal patterns were also found at the species level for the Labridae. Although high catches of many fishes were found just after new and full moons, peaks in abundance were also found at other times and therefore the model that patterns of input were fully explained by semi‐lunar or lunar cycles was rejected. Peaks in abundance, for some groups, were not concordant with semilunar or lunar periods but were found at times when the wind was strong and onshore. Thus, a combination of lunar phase and wind explained a greater proportion of variation in replenishment of reefs for some groups than lunar phase alone. Single physical variables, or combinations of them (based on multivariate analyses), explained variation in abundance of some groups (e.g. Labridae and Gobiidae), but there was still unexplained variation in the abundance of fish caught in nets. Multispecies models of larval supply were generally inadequate and it was concluded that unexplained variation in fish abundance was partly due to pooling fish at the level of family and above (e.g. total reef fishes), when resolution at the species level is required. It is argued that a knowledge of production of fish (spawning/hatching), length of presettlement phase, swimming abilities and behaviour, as well as the biological and physical phenomena influencing survival, are required to explain variation in the replenishment of reefs.
Feeding of larval blue whiting and Atlantic mackerel: a comparison of foraging strategies
Authors: Hillgruber N. , Kloppmann M. , Wahl E. , von Westernhagen H.
Published: June 2006

Fish larvae employ different feeding strategies depending on area and season of spawning and hatching of larvae. Feeding and growth of larvae of blue whiting Micromesistius poutassou and mackerel Scomber scombrus from Porcupine Bank and the Celtic Shelf Break, west of Ireland, were compared based on prey concentrations in the environment and larval feeding behaviour. Both species were adapted to different environmental conditions. The mesopelagic blue whiting spawned in oceanic water that was well mixed. It was characterized by low production and low prey densities with minimum prey densities <1.0 organism 1−1. Larvae of the Atlantic mackerel hatched later in the season in more productive water that was well stratified. Prey densities in the mackerel environment reached up to 1001−1. Blue whiting larvae displayed a rather random distribution in the water column. Mackerel larvae <7 mm standard length (Ls) were concentrated above the thermocline, while larvae >7 mm traversed the thermocline into deeper layers. Mackerel larvae >5mm Ls displayed marked cannibalism, exceeding 70%. Daily ration calculated on the basis of gut contents was rather low in both species: between 2.6 and 5.0% in blue whiting, but only 0.6 to 5.4% in mackerel. The results are discussed in relation to the respective environment both species encounter during their early larval life.
Early life history of herring larvae in contrasting feeding environments determined by otolith microstructure analysis
Authors: Folkvord A. , Rukan K. , Johannessen A. , Moksness E.
Published: June 2006

Newly hatched autumn‐spawned herring larvae Clupea harengus were released in two 2500‐m3 outdoor mesocosms and reared over a 2‐month period. Hydrographic conditions were similar in the two mesocosms, but the average plankton density was initially more than 10 times higher in mesocosm B compared to mesocosm A (>11−1v. <0.11−1). Half‐way through the experiment the feeding conditions reversed with three times higher average densities in mesocosm A than in mesocosm B (>31−1v.∼11−1). Herring larvae were sampled with a 0.3‐m2 two‐chambered net twice weekly, and survivors were harvested by draining the mesocosms at the end of the experiment. Otolith growth trajectories of individual larvae were determined by relating radial otolith size with number of increments from the outer edge of the otolith (days before capture). The increment widths during the first 3 weeks after hatching, including the first‐check size, were generally wider among larvae from mesocosm B (relatively good initial feeding conditions) than among those from mesocosm A (poor initial feeding conditions). The otolith growth pattern also confirmed that the surviving herring in mesocosm A belonged to the upper size range of larvae in the mesocosm after only 2–3 weeks from hatching; no such trend was found in mesocosm B. In both mesocosms the otolith size‐at‐age indicated that with the present sampling gear, herring larvae larger than 20–25 mm were underrepresented in the net samples. The information obtained from otolith‐size‐at‐age is compared with other morphometric and biochemical measures of size and condition of larvae obtained throughout the experiment.
Patterns in vendace recruitment in Lake Pyhäjärvi, south‐west Finland
Authors: Helminen H. , Sarvala J. , Karjalainen J.
Published: June 2006

A vendace Coregonus albula population has long formed the basis of a flourishing fishery in Lake Pyhäjärvi, south‐west Finland. Between 1971 and 1990, it exhibited variations in year‐class strength generally characterized by a 2‐year cycle of alternating strong and weak year classes, which implied density‐dependent regulation probably due to asymmetrical food competition between age groups. The abundance of piscivorous predators in the lake and the wanning of water after the hatching of larvae in spring together determined the final year‐class strength of vendace. Since 1990, year‐class sizes have remained very low and the 2‐year cycle has been disrupted. The continuously low levels of recruitment could not be explained by an increased larval mortality, although the decline started with 2 successive years with very high mortality of this life stage which reduced the whole spawning stock to a fraction of earlier levels, and consequently led to low larval numbers such that between 1988 and 1996 larval abundance was positively correlated with the spawning stock size. The importance of the spawning stock size to recruitment could also be seen in the whole 26‐year time series as a significant correlation between year‐class sizes with a 2‐year lag. The observed recruitment patterns of the vendace stock in Lake Pyhäjärvi thus show the importance of spawning stock size, intraspecific competition, predator effects and abiotic environmental variation.
Nutritional condition and vertical distribution of Baltic cod larvae
Authors: Grønkjær P. , Clemmesen C. , St. John M.
Published: June 2006

Newly hatched Baltic cod Gadus morhua larvae are typically found at depths >60 m. This is a region of low light and prey availability, hence generating the hypothesis that larvae have to migrate from hatching depth to the surface layer to avoid starvation and improve their nutritional condition. To test this hypothesis, Baltic cod larvae were sampled during the spawning seasons of 1994 and 1995 with depth‐resolving multiple opening/closing nets. Each larva was aged by otolith readings and its RNA/DNA ratio was determined as a measure of nutritional condition. The RNA/DNA ratios of these larvae aged 2‐25 days (median 10 days) ranged from 0.4 to 6.2, corresponding to levels exhibited by starving and fast‐growing larvae in laboratory calibration studies (starvation, protein growth rate, Gpi= ‐12.2% day−1; fastgrowing larvae, Gpi=14.1%day−1) respectively. Seventy per cent of the field caught larvae had RNA/DNA ratios between the mean values found for starving and fed laboratory larvae. Only larvae aged 8‐11 days had higher mean RNA/DNA ratios above 45 m than below (t‐test, P<0.05). However, the instantaneous protein growth rates were significantly higher for all larval age groups in the surface layers (t‐test, P<0.05). Starving larvae were found in all depths sampled (10‐85 m), whereas growing larvae (positive Gpi) were restricted to samples taken shallower than 45 m. These superior growth rates above 45 m corroborate the hypothesis and imply that migration to the shallow water layers is a prerequisite for good nutritional condition, growth and survival of Baltic cod larvae. The frequent occurrence of cod larvae older than 8 days in the deep water in poor condition suggests that a proportion of the larvae will die from Starvation in the deep layers of the Baltic Sea.
Interannual variations in condition indices of larval Norwegian spring‐spawning herring
Authors: Blom G. , Folkvord A. , Johannessen A. , Fossum P.
Published: June 2006

The sea water temperature off the Norwegian coast was lower in 1994 than in 1992 and 1993. RNA/DNA ratios of Norwegian spring spawning herring increased with increasing larval dry weight all years, except for larvae sampled south of 62°N in 1994. The RNA/DNA ratios indicated that each year, only a small portion ( 0.7%) of the larvae were starving. RNA/DNA ratios and temperature were negatively correlated in 1992, but in other years no significant correlations were found. Residuals of In RNA v. In DNA and In W v. Ls were poorly correlated in all years, but residuals of In RNA v. In DNA and In DNA v. In W were negatively correlated in all years. Principal component analysis showed that the RNA/DNA ratio and DNA (% of weight) were correlated with different axes. Abundance data for herring at the early larval and 0‐group stages in 1992–1994 indicated higher mortality in 1994 compared with the other years. The data do not indicate that average larval condition was poorer in 1994 than in other years. However, the variability in larval condition was higher in 1994 than in other years, and the condition of later larval stages was relatively lower in 1994 than in other years.
SOME APPLICATIONS OF THE DRUM AND CABLE IN A BRICK PLANT
Authors: Twells Robert
Published: June 2006

Application of the drum and cable in a brick plant, for plowing and scraping the shale, for transferring it to the driers and out again and for carrying the burned bricks to the freight cars are described. The devices are simple and cheap, but they have effected a great saving and have made it much easier to get the necessary labor.
A MERCURY VOLUMETER1
Authors: Goodner Ernest F.
Published: June 2006

A new volumeter using mercury as the liquid for determining volumes of solids.

Existing volumeters.—The eight principal volumeters which have been in use during the past few years are discussed, the disadvantages and advantages being pointed out and the requisites of a satisfactory voltmeter are outlined.

Description of new mercury voltmeter.—The volumeter consists of a burette which may be raised or lowered by means of a rack and pinion. To the lower end of the burette there is a rubber tube attached which connects at the other end with a reservoir. This reservoir is at a fixed point, level with the bottom of the burette when raised to its highest point and is partially filled with mercury. The whole volumeter is, in action, a large “U”‐tube with one movable limb (the burette). The volume is obtained by placing the briquette in the reservoir, causing a rise in the level of the mercury in both limbs of the “U”‐ tube. The burette is then lowered until the mercury has resumed its former level, this movement being the measure of the volume which is read directly from the graduations on the burette.

Mathematical analysis.—It is shown that a ratio of 1:1 of the reservoir and burette areas of free mercury surface will enable the reading of volumes as accurately as one can obtain the burette reading.

Comparative tests with other voltmeters.—Tests of the action of mercury, water and kerosene show that they behave alike in obtaining volumes. No saturation of burned or dry briquettes is necessary when using mercury as the liquid. Volumes with pycnometer and overflow types of volumeters checked those obtained with mercury volumeter to within 5/100 a cc.

Per cent variation of readings.—Results of three operators working independently indicate that for volumes above 25.00 cc. the volumeter is consistent within 0.2 per cent which is also the accuracy of the result.

Disadvantages.—1. The initial cost of about two pounds of mercury. 2. The slight tendency of the mercury to remain in cracks and holes of some briquettes, although readily shaken back into the reservoir. 3. A slight difficulty in obtaining the reading for the first dozen determinations.

Advantages.—1. No 12‐hour soaking in kerosene is necessary for dry briquettes. 2. There is no draining of briquettes after immersion. 3. No draining of liquid is necessary. 4. It is direct reading. 5. It is very speedy and accurate. 6. No adjustment is necessary before each volume is taken, and, when adjustment is required, it is very quickly accomplished. 7. There is no adjusting of ground glass stoppers.
THE COMPOSITION OF BARIUM GLASS1
Authors: Montgomery Robert J.
Published: June 2006

In this paper the relation between the composition of barium glasses and the optical constants is discussed as well as the general rules for proportioning batches. The important results and conclusions are given by the figures. After the required amounts of BaO and B2O3 have been obtained from figures 2 and 3, the amount of SiO2 can be obtained from figure 5, the alkali and ZnO from figure 7 and the Al2O3 from figure 8. If the total exceeds 100, the ZnO and the Al2O3 may be reduced. The proportions cannot be as definitely expressed as in the case of lead glasses and more experience is required to enable one to change the optical properties at will.
CORDS AND SURFACE‐MARKINGS IN GLASSWARE1
Authors: Wright F. E.
Published: June 2006

In the manufacture of glassware it is important to distinguish between surface‐markings and cords, both of which are serious defects and detrimental to quality. To do this immerse the piece of glass under test in a liquid of the same refringence and sight through liquid and glass toward a distant light. Under these conditions surface‐markings disappear altogether. Cords, on the other hand, stand out more distinctly than before.

The relative refringence of a cord compared with that of the adjacent glass can also be determined at the same time. For ordinary crown glasses monochlorbenzene is suggested as an immersion liquid. To lower its refractive index add benzene; to raise it add carbon bisulfide or monochlornaphthalene.
ZIRCONIA CEMENTS1
Authors: Sheppard By Mark
Published: June 2006

The effect of calcined zirconia on zirconia cement. Seven refractory cements were made having compositions of zirconia 90 per cent and plastic clay 10 per cent. (1) The shrinkage was found to be excessive in a cement containing raw zirconia and clay. The addition of 50 per cent or more of calcined zirconia practically eliminated this shrinkage and the cracking which accompanies it.(2)Strength Draw trials showed that the cement became strong at 1200°C and that it was very strong when burned at 1700°C. (3)Load tests on piers at 1500°C showed that joints of these cements did not fail in any manner at this temperature. (4) An industrial test of zirconia cement used as a wash for bungs in a malleable iron furnace showed that the life of a bung was increased about 25 per cent by the use of a zirconia wash.
THE APPLICATION OF PRODUCER GAS TO PERIODIC MUFFLE KILNS1
Authors: Ortman F. B.
Published: June 2006

Specific Installation.—Describes installation of Underwood System to six terra cotta kilns at plant Northwestern Terra Cotta Company.

Conclusions from operating data.—(1) Raw producer gas can be successfully applied to periodic muffle kilns. (2) There is little or no direct fuel economy over direct firing. (3) There is no labor economy unless the installation be large enough to justify mechanical coal and ash handling devices. (4) When interest on investment, depreciation and all other pertinent factors are taken into account, it is not likely that any great economy would be affected on periodic kilns over direct fire methods.

Advantages.—They are: (a) Somewhat better control of combustion gases and kiln temperatures. (c) Cleaner and more orderly kiln yard. (d) Abatement of smoke nuisance, particularly important in large cities.
HIGH FIRE PORCELAIN GLAZES1
Authors: Sortwell H. H.
Published: June 2006

Field covered.—The glazes studied covered the field 3.0 to 13.0 equivalents SiO2 and 0.3 to 3.25 equivalents A12O3 between the A12O3:SiO2 ratios of 1:4 and 1:20. The RO was maintained at 0.7 CaO and 0.3 K2O.

Deformation temperatures.—The deformation temperatures were determined by cones in a small gas furnace heated at the rate of 5O°C per hour. The deformation temperatures are shown graphically by isotherms. The results of the part of the field previously covered by Stull and Howat agree with their work. It was found that there is a deformation eutectic axis at a slight inclination to the ordinate representing A12O2 up to 7.0 equivalents SiO2. Above 7.0 equivalents the inclination rises, and at 11.0 equivalents SiO2 it increases much more.

Firing tests.—The glazes were applied to porcelain cups biscuited at cone 08, and fired to cones 10, 12, 14 and 16. The cone 10 test was made only for comparison, since Stull and Howat had previously covered a small part of the field at cones 9 and 11.

The glazes are plotted both by empirical formulas and batch weights, showing the location of the best glazes at the different temperatures.

In agreement with Stull's statement, increase in Al2O3 in this type of glaze decreases crazing.

Increase in SiO2 will not decrease crazing but if carried far enough will cause crazing to occur.

From cone 12 to cone 16 the best glazes have A12O3 and SiO2 contents corresponding to the approximate formula A12O3= 0.3 + 1/12 SiO2.
ANCIENT AND MODERN METHODS OF GLASS MANUFACTURE*
Authors: Dixon H. L.
Published: June 2006

Progress in appliances and methods of glass manufacture since 1877.— The article contains a brief summary of the personal experiences and observations of one who for over forty years has actively participated in the development of appliances and methods used in various branches of the glass industry.
THE USE OF PLASTIC CLAY GROG IN PREVENTING SPALLING1
Authors: Howe Raymond M. , Phelps Stewart M.
Published: June 2006

Effect of calcined clay grog on the properties of fire‐brick.—A medium dense‐burning clay was calcined at cone 8, then ground and mixed with plastic clay in various proportions up to 40 per cent. An air spalling test of the burned bricks showed that the grog increased the resistance to spalling about 5 per cent for each per cent of grog added. The results for other physical properties agreed with those found by previous observers; the bricks with grog were more porous and weaker mechanically but showed less drying and burning shrinkage.
NORMAL CONSISTENCY OF SANDED GYPSUM PLASTER1,2
Authors: Emley W. E , Faxon C. F.
Published: June 2006

Variation of tensile strength of sanded gypsum plasters with composition and consistency before setting.—To each of a series of 12 plasters, containing various proportions of sand, 5 different amounts of water were added. The consistencies, determined by means of a Southard viscosimeter, and the tensile strengths of the set plasters are tabulated. The results vary both with the kind of gypsum and with the fineness of the sand.

Suggested method of determining normal consistency of sanded gypsum plasters.—As a result of considerable experience the authors have reached the conclusion that material of the proper consistency to be used for plastering will show a slump of 1/2 inch when tested in the Southard viscosimeter.
THE NEW FACTORY OF THE MONONGAH GLASS COMPANY
Authors: Tillotson E. Ward
Published: June 2006

This new factory, constructed in 1918‐19, is worthy of note by reason of its expensive (7 to 8 hundred thousand dollars per unit) and permanent construction, by reason of the high quality of glass produced in continuous tanks, and by reason of its efficient design and arrangement and the extensive employment of mechanical devices throughout. This paper gives a detailed description of the factory under the following headings: Historical; Buildings, Warehouse, and Factory; The Hardford ‐ Fairmont Feeder with description operation; The Batch System and the Batch; The Stacks; The Laboratory; and Selecting and Packing the Ware.
ELECTRICALLY HEATED GLASS ANNEALING LEHR1
Authors: Collins E. F.
Published: June 2006

Time‐temperature data relating to relaxation of stresses.—Existing time‐temp, data covering the relaxation of stresses in annealing of glass has been assembled. Range, control, and distribution of temp. are important factors in annealing. The annealing time was reduced from 5 to 2.3 hours when temp. var. was reduced from 10° to 2.5°C, in the case of one glass whose annealing temp. was 476°.

Electric heat secures perfect anneal in shortened time.—Electric heat with its automatic control holds temp. within +0.6 per cent in ranges required for annealing, as shown by tests, even when the temp. changes 23° per hour and when the annealing treatmat (as for optical glass) covers a month in time.

Vertical Lehr superior to horizontal type.—Electrically heated lehrs of horizontal and vertical types are discussed. The vertical lehr offers many apparent advantages and a higher thermal efficiency. A particular lehr of 500–600 Ibs. ware capacity per hour, shows efficiencies in ratio of 6 to 10 in favor of electric lehr of vertical type. Tests made on an electrically heated vertical lehr annealing high grade ware showed a reduction in cost of manufactured part of 20 per cent, or more than 75 times total cost of electric power consumed.
SOME DATA ON THE COMPOSITION OF ARSENIC ENAMELS FOR COPPER1
Authors: Sweely B. T.
Published: June 2006

Methods of application are by usual wet slushing, and sieving powdered enamel on to clean copper sheets and fusing to a smooth coat. Where slush‐coat is necessary it is advisable to use an enamel free from lead and arsenic as a ground. In this work the dry method is used exclusively. In the formulae given, increase of SiO2, increases fracturing or shivering, increase of B2O3 above 0.2 equiv. in presence of 0.1 equiv. AS2O3 causes enamels to come mat. Increasing KNaO at expense of PbO decreases opacity, improves fit and gloss, but makes enamel more soluble. The following limits in composition are recommended: 0.3 to 0.7 KNaO, 1.3 to 1.8 SiO2, 0.7 to 3 PbO, 0.0 to 0.2 B2O3, 0.05 to 0.15 AS2O3.