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doi: 10.1093/icesjms/46.1.16pmid: N/A
A 17-year record (1964–1980, 204 observations) of monthly catches of pilchard (Sardina pilchardus) from Greek waters was analysed using AutoRegressive Integrated Moving Average (ARIMA) techniques (Box and Jenkins, 1976). Two models were found to be suitable for describing the dynamics of the fishery and for forecasting up to 12 months ahead:Xt=Xt−1+Xt−12−Xt−13+et−0.539et−12−0.289et−1+0.156et−13andX1=Xt−1+Xt−12−X1−13+et−0.537et−12−0.391et−1+0.21et−13−0.255et−2+0.137et−14,where Xt = landings in month t, and et = error term in month t. Forecasts were compared with actual data for 1981 that were not used in the estimation of the parameters of either model. Mean error was 14.6% and 12 % for the two models, respectively. This suggests that ARIMA procedures are capable of describing and forecasting the complex dynamics of the Greek pilchard fishery, which have hitherto been regarded as difficult to predict owing to the strong influence of year-to-year changes in oceanographic and biological conditions and socio-economic factors (low commercial value and demand, high discard rate).
doi: 10.1093/icesjms/46.1.24pmid: N/A
Reproductive biology of haddock (Melanogrammus aeglefinus L.) from the Nova Scotia shelf was investigated, including size at maturity, gonadal development, and oocyte size distribution at different stages of maturity. Gonad development reaches a maximum in February and March, with peak spawning occurring between March and May. The gonadosomatic index reaches a maximum of between 10 and 15% of body weight in mature fish.The minimum diameters of oocytes that would be spawned in the current year were identified as 0.212 mm and 0.155 mm for “ripe” and “almost ripe” fish. All oocytes spawned by “running ripe” fish were over 0.250 mm in diameter.The relationship between number of oocytes to be spawned in the current year and fish length was determined as:number of oocytes = 962.64 × FL1.64,where FL is fork length in cm. The equivalent relationship between total number of oocytes (> 0.1 mm in diameter) and fish length was:number of oocytes = 119.51 × FL2–30.
doi: 10.1093/icesjms/46.1.35pmid: N/A
The maturation of North Sea plaice is studied on the basis of two research-vessel surveys and market-sampling data from the commercial fisheries. In female plaice the juvenile-adult transition occurred between May and September. Development of the female gonad took place between July and December, although the gonad did not gain weight before October. Gonad weight reached a maximum of circa 17% of the gutted body weight between January and March. The average female plaice was in spawning condition for about five weeks from late January to early March. Male plaice were in spawning condition for at least 11 weeks from the second half of December to the second half of March. In females the start of spawning was earlier in older fish, but the end of spawning did not differ between age groups. In males spawning ended later in older fish. The time that mature plaice were in spawning condition increased with the age of the fish in males and females. During the spawning season mature plaice hardly fed. Spent fish resumed feeding in January. The cessation of feeding in mature plaice was not related to the absence of food.Male plaice became sexually mature as II- and Ill-group, females as IV- and V-group. Length at 50% maturity (L50) was 22 cm and 34 cm for males and females respectively. L50 and age at 50% maturity (A50) differed between geographical areas, increasing from south to north. Annual differences were observed in L50 and A50 which were related to annual differences in growth rate. Slower-growing plaice reached maturity at a smaller length but higher age than faster-growing plaice. Comparison with published data shows that at present both male and female plaice mature at a younger age and at a smaller size than at the beginning of this century.
Holliday, D. V.; Pieper, R. E.; Kleppel, G. S.
doi: 10.1093/icesjms/46.1.52pmid: N/A
The theoretical basis for using multiple acoustic frequencies in the assessment of the distributions of small zooplankton (ca. 0.1 mm to 10 mm in length) is discussed. One practical implementation of this theory is the Multifrequency Acoustic Profiling System (MAPS). The MAPS uses 21 discrete frequencies in the band between 100 kHz and 10 MHz. Acoustic data collected with this system are transformed to plots of zooplankton abundance versus size and depth for individual casts. Acoustic estimates of abundance versus size for individual casts are combined to illustrate two-dimensional spatial distribution and temporal variations. These patterns are compared with data collected at the same time for temperature, salinity, and chlorophyll fluorescence. Illustrations from several contrasting environments are included.Nous discutons les raisons théoriques pour l'utilisation de fréquences acoustiques multiples pour 1'èvaluation des distributions de zooplancton (ca. 0.1 à 10 mm de longueur). Un usage pratique de cette théorie est le Multifrequency Acoustic Profiling System (MAPS). Le MAPS utilise 21 fréquences séparées dans la bande entre 100 kHz et 10 MHz. Nous transformons les données acoustiques récoltées avec ce système en graphes d'abondance de zooplancton contre leurs dimensions et contre la profondeur de mises-a-1è individuelles. Les estimations acoustiques d'abondance contre leurs dimensions pour les mises-à-l'eau individuelles sont combinées pour illustrer la distribution spatiale en deux dimensions et les variations temporelles. Ces résultats sont comparés avec les données de température, de salinité, et de fluorescence de la chlorophylle recueillies simultanément. Des exemples de plusieurs environnements différents sont inclus.
Nedreaas, Kjell; Nævdal, Gunnar
doi: 10.1093/icesjms/46.1.76pmid: N/A
In the present paper the three redfish species, Sebastes marinus, S. mentella, and S. viviparus, are compared by use of electrophoretic studies of haemoglobins and 17 enzymes in white muscle, liver, and eye tissue. Some enzymes are also studied in heart tissue. The aims of the investigation are to study the validity, relationships, and geographical distribution of the species and to reveal characteristics to be used for species identification of 0- and 1- group fish which cannot be identified by morphological traits. In some areas adult specimens, especially s. marinus and S. mentella, may also be extremely difficult to identify. Generally the species are very similar in most enzyme patterns.S. viviparus may be identified by malate dehydrogenase (MDH) in all four tissues, isocitrate dehydrogenase (IDH) from the eye, and malic enzyme (ME) from the liver. S. mentella can be separated from the others by haemoglobin patterns. In liver IDH both S. viviparus and S. marinus are polymorphic with clearly different frequency distributions, while S. mentella is monomorphic. In muscle ME S. mentella is polymorphic while S. marinus and S. viviparus are monomorphic. Variations in some other enzymes, probably polymorphisms, could also be seen, but either at very low frequencies or with electrophoretograms too weak for clear-cut typing of the specimens.
Hankin, David G.; Diamond, Nancy; Mohr, Michael S.; Ianelli, James
doi: 10.1093/icesjms/46.1.94pmid: N/A
A total of 12034 adult female Dungeness crabs ranging in carapace width from 91.6 to 172.9 mm were tagged and released in northern California waters. A molt increment regression line, based on 111 single- molt tag recoveries and 166 laboratory molting records, showed that average molt increments declined linearly from about 21 to 12 mm as carapace widths increased from 90 to 150 mm. Size-specific annual molting probabilities, estimated from shell-condition data, exceeded 0.90 for crabs with carapace widths less than 135 mm but then declined rapidly to near zero at carapace widths exceeding 160 mm. Estimated annual survival rates averaged 0.11 for crabs exceeding 155 mm; survival rates for smaller crabs are probably greater, but could not be estimated. Tag-recovery data provided evidence that most adult females extrude egg masses annually, but that many do so without molting and mating; viable sperm may be retained for at least 2.5 years. Size-specific fecundities ranged from about 0.1 to 1.6 million eggs and were found to depend on previous molting history as well as on crab size. For individuals of similar size, crabs that had molted during the most recent season had greater fecundities than those that had not.
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