Age determination and age related factors in the teeth of Western North Atlantic bottlenose dolphins.

Teeth were taken from 120 bottlenose dolphins, Tursiops truncatus, which had stranded on the mid-Atlantic coast of the United States. The number of annual growth layer groups (GLGs) for each animal was used to construct a growth curve. The growth rate of coastal North Atlantic Ocean Tursiops is similar to other cetaceans in having a high initial rate of growth, with no differences in growth between females and males. In females, the first dentinal GLG is thickest and is followed by GLGs which become progressively narrower. In males, the second GLG is thicker than the first; GLGs beyond number two become progressively smaller but at a slower rate than in females. In males and females, the translucent layer makes up proportionally larger parts of the GLG as the animal ages, but in males the percent translucent layer remains constant at about 50% while in females it continues to increase up to about 70% of the GLG. These two factors, GLGs width and translucent layer width, indicate that the sex and age of the animal influence the deposition of GLGs. Incremental layers are also present, averaging 12 per GLG, and seem similar to incremental layers described in other marine mammals. A plot of the relationship of percent growth of the last GLG to time of death suggests that the deposition of GLGs is relatively constant, at least during the first half of the year, and that North Atlantic Ocean Tursiops give birth in the fall as well as in the spring. (PDF contains 31 pages.)

Espacio e identidad en un "western" crepuscular: The Misfits

Raquel Merino Álvarez, José Miguel Santamaría, Eterio Pajares (eds.)

Field guide to requiem sharks (Elasmobranchiomorphi: Carcharhinidae) of the Western North Atlantic

Identification problems are common for many sharks due to a general lack of meristic characteristics that are typically useful for separating species. Other than number of vertebrae and number and shape of teeth, identifications are frequently based on external features that are often shared among species. Identification problems in the field are most prevalent when live specimens are captured and releasing them with a minimum of stress is a priority (e.g., shark tagging programs). Identifications must be accurate and conducted quickly but this can be challenging, especially if specimens are very active or too large to be landed without physical damage. This field guide was designed primarily for use during field studies and presents a simplified method for identifying the 21 species of western North Atlantic Ocean sharks belonging to the family Carcharhinidae (carcharhinids). To assist with identifications a dichotomous key to Carcharhinidae was developed, and for the more problematic Carcharhinus species (12 species), separation sheets based on important distinguishing features were constructed. Descriptive text and illustrations provided in the species accounts were developed from field observations, photographs, and published references. (PDF file contains 36 pages.)

Distribution, relative abundance and developmental morphology of paralarval cephalopods in the Western North Atlantic Ocean

Paralarval and juvenile cephalopods collected in plankton samples on 21 western North Atlantic cruises were identified and enumerated. The 3731 specimens were assigned to 44 generic and specific taxa. This paper describes their spatial and temporal distributions and their developmental morphology. The smallest paralarvae recognized for a number of species are identified and illustrated. The two most abundant and most frequently collected taxa were identifiable to species based on known systematic characters of young, as well as on distribution of the adults. These were the neritic squids Loligo pealeii and Illex illecebrosus collected north of Cape Hatteras, both valuable fishery resources. Other abundant taxa included two morphotypes of ommastrephids, at least five species of enoploteuthids, two species of onychoteuthids, and unidentified octopods. Most taxa were distributed widely both in time and in space, although some seasonal and mesoscale-spatial patterns were indicated. The taxa that appeared to have distinct seasonal distribution included most of the neritic species and, surprisingly, the young of the bathypelagic cranchiids. In eight seasonal cruises over the continental shelf of the middle U.S. Atlantic states, neritic taxa demonstrated approximately the same seasonal patterns during two consecutive years. Interannual differences in the oceanic taxa collected on the shelf were extreme. The highest abundance and diversity of planktonic cephalopods in the oceanic samples were consistently found in the vicinity of the Gulf Stream. Only eight of the oceanic taxa appeared to have limited areal distributions, compared with twelve taxa that were found throughout the western North Atlantic regions sampled in this study. Many taxa, however, were not collected frequently enough to describe seasonal or spatial patterns. Comparisons with published accounts of other cephalopod surveys indicate both strengths and weaknesses in various sampling techniques for capturing the young of oceanic cephalopods. Enoploteuthids were abundant both in our study and in other studies using midwater trawls in several areas of the North Atlantic. Thus, this family probably is adequately sampled over its developmental range. In contrast, octopoteuthids and chtenopterygiids are rare in collections made by small to medium-sized midwater trawls but are comparatively common in plankton samples. For families that are relatively common in plankton samples, paralarval abundance, derived similarly to the familiar ichthyoplankton surveys of fisheries science, may be the most reliable method of gathering data on distribution and abundance. (PDF file contains 58 pages.)

Pictorial Guide to the Groupers (Teleostei: Serranidae) of the Western North Atlantic

This guide was developed to assist with the identification of western North Atlantic grouper species of the genera Alphestes, Cephalopholis, Dermatolepis, Epinephelus, Gonioplectrus, Mycteroperca, and Paranthias. The primary purpose for assembling the guide is for use with projects that deploy underwater video camera systems. The most vital source of information used to develop the guide was an archive of underwater video footage recorded during fishery projects. These video tapes contain 348 hours of survey activity and are maintained at the National Marine Fisheries Service (NMFS), Pascagoula, Mississippi. This footage spans several years (1980-92) and was recorded under a wide variety of conditions depicting diverse habitats from areas of the western North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. Published references were used as sources of information for those species not recorded on video footage during NMFS projects. These references were also used to augment information collected from video footage to provide broader and more complete descriptions. The pictorial guide presents information for all 25 grouper species reported to occur in the western North Atlantic. Species accounts provide descriptive text and illustrations depicting documented phases for the various groupers. In addition, species separation sheets based on important identification features were constructed to further assist with species identification. A meristic table provides information for specimens captured in conjunction with videoassisted fishery surveys. A computerized version enables guide users to amend, revise, update, or customize the guide as new observations and information become available. (PDF file contains 52 pages.)

Field Guide to the Searobins (Prionotus and Bellator) in the Western North Atlantic

Species identifications of Prionotus and Bellator are often difficult under field conditions owing to the large number of species and their overlapping taxonomic characteristics. This key is intended to provide a simplified, accurate means to identify adult searobins greater than 10 cm standard length. All recognized species from the western North Atlantic, the Gulf of Mexico, and Caribbean Sea are included. (PDF file contains 30 pages.)

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.

Estimating abundances of 0-group western Baltic cod by using pound net fisheries

Nearshore 0-group western Baltic cod are frequently caught as bycatch in the commercial pound net fishery. Pound net fishermen from the Danish Isle of Funen and Lolland and the German Isle of Fehmarn have recorded their catches of small cod between September and December 2008. Abundance patterns were analysed, particularly concerning the influence of abiotic factors (hydrography, meteorology) and the differences between sampling sites. Catch per unit effort (CPUE) differed by site and location, whereas CPUE were highest at Lolland. Correlation between catch and wind/currents were generally weak. However, wind directions and current speeds seem to affect the catch rates. Finally an algorithm was developed to calculate a recruitment index for western Baltic cod recruitment success based on previous analyses.

WEFTA-Laborvergleichsuntersuchungen zur pH-Bestimmung in Fischerei-Erzeugnissen - Eine gemeinsame Aktion der Western European Fish Technologists' Association

12 samples (6 original samples and 6 diluted samples) were analysed by 14 WEFTA laboratories for their pH values in an inter-laboratory comparison exercise. As a result it can be stated that the majority of participating laboratories could determine the pH values very exactly. The pH values obtained are ranging only little around the calculated mean (less than 0.1 pH unit). It could also be demonstrated that the participating institutes could analyse both, pH values in fishery products and aqueous salt solutions. However, also in this exercise a number of outliers and deviating values have been detected. Therefore it is of utmost importance to calibrate the pH electrodes in regular intervals and to maintain them carefully. Intra-laboratory comparison measurements are recommended to detect weak points.

27. Jahrestagung der WEFTA (Western European Fish Technologists’ Association)

Die 27. Jahrestagung der WEFTA fand vom 20.-22.10.1997 in Madrid, Spanien, statt. Organisiert wurde diese WEFTA-Tagung von J. Boderias und den Mitarbeitern des Instituto des Frio in Madrid. Das Interesse an dieser WEFTA-Tagung war besonders groß, dies zeigte sich insbesondere an der Anzahl der angemeldeten Vorträge und Poster sowie an den ca. 130 gemeldeten Teilnehmern aus 16 WEFTA - Mitgliedstaaten und Gästen aus den USA, Argentinien, Israel, Lettland, Mexiko und Venezuela.

26. Jahrestagung der WEFTA (Western European Fish Technologists´ Association) in Gdynia, Polen

Die 26. Jahrestagung der WEFTA fand vom 22. bis 26. September 1996 erstmalig in Polen statt. Gastgeber war P. Bykowski vom Institut für Seefischerei (MIR) in Gdynia, das im Jahre 1996 sein 75jähriges Jubiläum feiern konnte . Die Tagung wurde von etwa 70 Delegierten aus den 16 WEFTA Mitgliedsstaaten und Gästen aus den USA, Rußland, Israel und Litauen besucht. Die Konferenz wurde von Z. Polanski, dem Direktor des Institutes und von M. Brzeski, dem Zweiten Bürgermeister der Stadt Gdynia eröffnet. In 10 Vortragssektionen und einer Postersektion wurden den Teilnehmern insgesamt 38 Vorträge und 24 Poster geboten.

A mathematical study of finite-amplitude rock-folding

The problem of the finite-amplitude folding of an isolated, linearly viscous layer under compression and imbedded in a medium of lower viscosity is treated theoretically by using a variational method to derive finite difference equations which are solved on a digital computer. The problem depends on a single physical parameter, the ratio of the fold wavelength, L, to the "dominant wavelength" of the infinitesimal-amplitude treatment, L_d. Therefore, the natural range of physical parameters is covered by the computation of three folds, with L/L_d = 0, 1, and 4.6, up to a maximum dip of 90°.

Significant differences in fold shape are found among the three folds; folds with higher L/L_d have sharper crests. Folds with L/L_d = 0 and L/L_d = 1 become fan folds at high amplitude. A description of the shape in terms of a harmonic analysis of inclination as a function of arc length shows this systematic variation with L/L_d and is relatively insensitive to the initial shape of the layer. This method of shape description is proposed as a convenient way of measuring the shape of natural folds.

The infinitesimal-amplitude treatment does not predict fold-shape development satisfactorily beyond a limb-dip of 5°. A proposed extension of the treatment continues the wavelength-selection mechanism of the infinitesimal treatment up to a limb-dip of 15°; after this stage the wavelength-selection mechanism no longer operates and fold shape is mainly determined by L/L_d and limb-dip.

Strain-rates and finite strains in the medium are calculated f or all stages of the L/L_d = 1 and L/L_d = 4.6 folds. At limb-dips greater than 45° the planes of maximum flattening and maximum flattening rat e show the characteristic orientation and fanning of axial-plane cleavage.

Exploratory survey of Malian and Ndururu traps in River Rima, north western Nigeria

The fabrication and operational techniques of Malian and Ndurutu traps mostly used by the fishermen in River Rima in north western Nigeria were evaluated through structured questionnaire and measurement of samples of the Data collected were analyzed using descriptive statistics. There was no standard in the dimensions of either of the traps. The traps were made of locally sourced materials, except the synthetic net of the Malian trap. About 81 and 80% of the respondents fabricated their Malian and Ndurutu traps, respectively. The major problems encountered in the structure and operation of the Malian trap included projection above water, stealing of catches and trap, and trapping of small sized fishes as indicated by 61.9, 47.6 and 28.6% of the respondents, respectively. In the case of the Ndurutu trap, 72.0, 48.0, 12.0 and 8.0% of the respondents respectively indicated poor durability, single entrance valve, destruction by cattle and instability in water, as the major problems encountered. As improvement measures for the Malian trap, the respondents suggested increase in number and size of valve (81.0%), horizontal positioning (57.1%) and square shape (47.6%) while 52.0% each suggested increase in number of entrance valve and netting of Ndurutu trap. The fishermen demonstrated ingenuity in the fabrication and operation of the traps, but they failed to initiate the required improvement. It is important to critically examine the designs, materials, costs and limitations of the traps and the suggestions of the fishermen, as basis for improvement on the technology of the traps

Evaluation of a new fishing pot trap (Lege) in River Rima, north western Nigeria

Based on the findings and diagnostic survey, a new fishing trap, christened Lege trap was designed and fabricated, and the performance evaluated. The 8-valve Lege trap was assessed concurrently with Malian and Ndurutu traps by the fishermen in the study area. The experiment was conducted in a randomized complete block design with one factor each replicated three times. Data collected on fish diversity number, biomass and size were subjected to descriptive statistics and analysis of variance. The results showed that 22 fish species belonging to thirteen families were caught. The prototype (Lege) trap recorded higher species diversity index (0.90) than the Malian (0.50) and Ndurutu (0.50) traps. The Lege trap also accounted for the largest number (55%) and biomass (63%) of fish caught which was significantly (P<0.05) higher than those of the Malian and Nduutu traps were. The mean length (15.03~c5.70cm), weight (60.43~c48.61g) and girth (4.77~c1.65cm) of fishes caught in the Lege trap were also significantly (P0.05) higher than those caught in the other two traps. These results demonstrated better performance of the new trap than the two conventional traps, even though the sizes of some of the fish species caught in all the traps were below those allowed by the Sokoto State Fisheries Edict where the study was conducted. Therefore, since it is desirable to develop conservation-oriented trap at a least cost, it is necessary to research further on the number of valves and mesh size of the new trap

Influence of number of valves on catch composition of a fishing pot trap (Lege) in River Rima, north western Nigeria

Three types of prototype (Lege) traps with different numbers of entrance valves were evaluated in River Rima, north western Nigeria. The traps contained 4,6 and 8 valves, tagged 4-V, 6-V and 8-V respectively. The experiment was carried out in a randomized complete block design with one factor each replicated three times. Data collected on fish diversity, number biomass and sizes were subjected to descriptive statistics and analysis of variance. The results of the catch composition showed close diversity index of 0.86 for 6-V, 0.80 for 8-V and 0.60 for 4-V Lege traps. However, the number (41%) and biomass 48%) of fish caught in the 6-V Lege trap were significantly (P0.05) higher than those caught in the other traps. There was no definite trend in the sizes (length and girth) of fish caught in the traps. On the basis of species diversity, and the number and biomass of fish caught, the 6-V Lege showed preference for adoption than the other two traps. However, further studies are recommended on the appropriate mesh size net for the trap in line with the provisions of fisheries edicts