Micronekton of the North Pacific

1. INTRODUCTION 1.1 Working Group History 2. SPECIES COMPOSITION AND DISTRIBUTION PATTERNS RELATED TO WATER MASSES 2.1 Mesopelagic Fishes 2.1.1 Dominant families 2.1.2 Large-scale feeding and/or spawning migration or expatriation? 2.1.3 Definition of water masses 2.1.4 Species composition 2.2 Crustacean Micronekton 2.2.1 Euphausiids 2.2.2 Mysids and decapods 2.3 Cephalopod Micronekton 2.3.1 Family Enoploteuthidae 2.3.2 Family Gonatidae 2.3.3 Family Onychoteuthidae 2.3.4 Family Pyroteuthidae 2.3.5 Other cephalopods 3. VERTICAL DISTRIBUTION PATTERNS 3.1 Mesopelagic Fishes 3.1.1 Significance of diel vertical migration 3.1.2 DVM patterns 3.1.3 Ontogenetic change in DVM patterns 3.2 Crustacean Micronekton 3.3 Cephalopod Micronekton 4. BIOMASS PATTERNS 4.1 Micronektonic Fish 5. LIFE HISTORY 5.1 Fish Micronekton 5.1.1 Age and growth 5.1.2 Production 5.1.3 Reproduction 5.1.4 Mortality 5.2 Crustacean Micronekton 5.2.1 Age and growth 5.2.2 Production 5.2.3 Reproduction and early life history 5.2.4 Mortality 5.3 Cephalopod Micronekton 5.3.1 Age and growth 5.3.2 Production 5.3.3 Reproduction and early life history 5.3.4 Mortality 6. ECOLOGICAL RELATIONS 6.1 Feeding Habits 6.1.1 Fish micronekton 6.1.2 Crustacean micronekton 6.1.3 Cephalopod micronekton 6.2 Estimating the Impact of Micronekton Predation on Zooplankton 6.2.1 Predation by micronektonic fish 6.3 Predators 6.3.1 Cephalopods 6.3.2 Elasmobranchs 6.3.3 Osteichthyes 6.3.4 Seabirds 6.3.5 Pinnipeds 6.3.6 Cetaceans 6.3.7 Human consumption 6.4 Predation Rate 6.5 Ecosystem Perspectives 6.6 Interactions between Micronekton and Shallow Topographies 7. SAMPLING CONSIDERATIONS 7.1 Net Trawling 7.1.1 Sampling gears 7.1.2 Sampling of surface migratory myctophids 7.1.3 Commercial-sized trawl sampling 7.1.4 Sampling of euphausiids and pelagic decapods 7.2 Acoustic Sampling 7.2.1 Acoustic theory and usage 7.3 Video Observations (Submersible and ROV) 8. SUMMARY OF PRESENT STATE OF KNOWLEDGE 8.1 Fish Micronekton 8.2 Crustacean Micronekton 8.3 Cephalopod Micronekton 9. RECOMMENDATIONS 10. REFERENCES 11. APPENDICES (122 page document)

Length-weight relationship and the diets of Clarias lazera (Cuvier and Valenciennes), family Clariidae (Osteichthyes: Siluriformes) in Zaria, Nigeria

The length-weight relationship and the diets of Clarias lazera were investigated between July 1981 and June 1982. About 450 specimens were examined. The standard lengths of the fish ranged from 8.5 cm to 42.2 cm. Significant differences were found between the standard lengths of the males and females with the latter slightly shorter. Somatic weights varied between 10 g to 502 g. Length-weight regression analysis gave a "b" value of 3.02 for both males and females combined; thus indicating an isometric growth. Analysis of the food in the stomachs showed that the fish is an omnivore although, it fed more on insects and fish than other food items

Algae from the inland ice of Greenland. [Translation from: Kongl.Vetenskaps-Akademiens Forhandlingar 1871(2) 293-296, 1871.]

On the large inland ice cover of Greenland, where the temperature even during the short summer, falls below freezing some time during the daily 24 hours, it is still possible to find organic life. The author found in melted ice water several species of algae on his ”walk” in the latter part of July 1870. The article describes the finds and tries to identify the algae to family level.

Chydoridae of the world's fauna. [Translation from: Fauna SSSR, Crustacea 1 (2), Nauka, Leningrad, 1971. ]

This translation presents identification keys to the subfamilies, genera, species and subspecies of Chydoridae of the USSR. Chydoridae are a family in the order of Cladocera.

Cultivation methods for Lemnaceae [Translation from: Wiadomosci Botaniczne 7(2) 153-164, 1963]

Representatives from the family of Lemnaceae (duckweed) make ideal experimental material for research into a succession of phytophysiological processes with regard to growth rate and vegetative reproduction. They are also easy to maintain in sterile cultures. Lemnaceae belong to the higher flowering plants (flowers are rarely produced), however they are distinguished by a much simplified morphological and anatomical structure. As water plants they possess the advantage, that they can be cultivated in synthetic media under laboratory conditions controlled by the application of both a known light intensity and temperature. This paper describes experimental research of growth of Lemnaceae in different conditions. Some of the variables were mineral media, illumination and aeration.

Length-weight relationships of five species of the family Sparidae in the Gulf of Guinea

Length-weight relationships are presented by sex and by country for five species of the family Sparidae (Pugrus caeruleostictus, Pagellus bellottii, Dentex canariensis, Dentex congonensis, Dentex angolensis) sampled in April 1990 during the Guinea '90 trawling survey off Sierra Leone, Liberia, Cote d'Ivoire and Ghana.

Descriptions of larval, prejuvenile, and juvenile finescale menhaden (Brevoortia gunteri) (family Clupeidae), and comparisons to gulf menhaden (B. patronus)

Larval and juvenile development of finescale menhaden (Brevoortia gunteri) is described for the first time by using wild-caught individuals from Nueces Bay, Texas, and is compared with larval and juvenile development of co-occurring gulf menhaden (B. patronus). Meristics, morphometrics, and pigmentation patterns were examined as development proceeded. An illustrated series of finescale menhaden is presented to show changes that occurred during development. For finescale menhaden, transformation to the juvenile stage was completed by 17−19 mm standard length (SL). By contrast, transformation to the juvenile stage for gulf menhaden was not complete until 23−25 mm SL. Characteristics useful for separating larval and juvenile finescale menhaden from gulf menhaden included 1) the presence or absence of pigment at the base of the insertion of the pelvic fins; 2) the standard length at which medial predorsal pigment occurs; 3) differences in the number of dorsal fin ray elements; and, 4) the number of vertebrae.

Distribution and co-occurrence of rockfishes (family: Sebastidae) over trawlable shelf and slope habitats of California and southern Oregon

The rockfishes of the sebastid genus Sebastes are a very important fishery resource off the coasts of California and southern Oregon. How-ever, many of the 54 managed stocks of west coast rockfish have recently reached historically low population levels, leading fishery managers to re-examine current management practices. Management of rockfish stocks as multispecies aggregates, as opposed to independent stocks within the ground-fish fishery, can be more desirable when nontargeted bycatch, discard, and management complexity are considered. Rockfish assemblage structure and species co-occurrences were determined by using data from the Alaska Fisheries Science Center triennial continental shelf bottom trawl survey. The weight of rockfish species in trawl catches was expressed as a catch-per-unit-of-effort (CPUE) statistic, from which species spatial distributions, overlaps, diversity, and richness were analyzed. Multidimensional scaling of transformed CPUE data was employed in indirect gradient and multivariate partitioning analyses to quantify assemblage relationships. Results indicated that rockfish distributions closely match the bathymetry of coastal waters. Indirect gradient analysis suggested that depth and latitude are the principal factors in structuring the spatial distributions of rockfish on trawlable habitat. In addition, four assemblages were identified through the joint evaluation of species’ distributions and multivariate partitioning analyses: 1) deep-water slope; 2) northern shelf; 3) southern shelf; and 4) nearshore. The slope, shelf, and near-shore groups are found in depth ranges of 200–500 m, 100–250 m, and 50–150 m, respectively. The division of northern and southern shelf assemblages occurs over a broad area between Cape Mendocino and Monterey Canyon. The results of this analysis are likely to have direct application in the management of rockfish stocks off the coasts of southern Oregon and California.

Sex ratio of the sole Euryglossa orientalis (Bl. & Schn.) (family: Soleidae) from the Karachi coast

This paper present a study on sex ratio and reveals segregation or aggregation of males and females in accordance with environmental conditions, the differential behaviour of sexes, and due to fishing.

A Guide to the freshwater fauna of Ceylon. Supplement 2

This is the second supplement to "A guide to the freshwater fauna of Ceylon" by A. S. Mendis and C. H. Fernando, Bull. Fish. Res. Stn., Ceylon, No. 12, 160 pp. (1962). In the present supplement additions and corrections are made in the sections on Protozoa, Annelida and Arthropoda. The sections on Platyhelrainthes and Nematoda have been expanded and the Acanthocephala added. A list of species recorded and the hosts of the parasitic forms are included. In the "Guide", the insects with only larval stages in aquatic habitats were mentioned only briefly and no species lists were included. In this supplement this gap is largely filled by added notes and inclusion of species lists of all these groups except the Neuroptera, Lepidoptera, Tabanidae, Syrphidae and Stratiomyidae. The orders Neuroptera and Lepidoptera have relatively few members in freshwater habitats and the families Tabanidae, Syrphidae and Stratiomyidae have forms with larvae in aquatic habitats and also in moist places which are not true freshwater habitats. At this time, it is not possible to separate those forms living in freshwater habitats. Short diagnoses of six additional families are given, namely, the ixidae, Psychodidae, Tabanidae Stratiomyidae, Rhagionidae and Sciomyzidae. Keys are provided for the Odonata and Ephermeroptera larvae down to the family level. An attempt has been made to make the references more comprehensive. Works dealing specifically with the Ceylonese fauna are of course included, but in addition those which are of use in diagnosis of local genera and species have been cited.

The hammerhead sharks in Ceylon seas (Family Sphyrnidae)

The present study confirmed the previous listing of this species in the tropical seas around Ceylon (Misra 1947, Munro 1955). Photographs of the ventral surface of the head are shown in Fig. 1 and the distinguishing characteristics of the head are noted in the key to the species.

Allometric study of skeleton weight, body weight and length relationship of Euryglossa orientalis (Bl. & Schn.) (Family: Soleidae) from Karachi coast

Present study deals with the family Soleidae (common sole) Euryglossa orientalis (Bl. & Schn.) of the order Pleuronectiformis from Karachi coast. Separate equation (regression line) for describing the length weight relationships for male and female combined are justified. Allometric studies were made on skeleton weight relative to the length and the weight of the fish. The regression equation 'a' and 'b' values of standard length/skeleton weight and body weight/skeleton weight are statistically significant.