ALBERT

Notes: The red bandfish Cepola rubescens is characterized by a normal gonochoristic sexual organization. The overall male: female ratio did not differ significantly (x2=4.57, P〈0.05) from the theoretical 1: 1. However, the male: female ratio differed with season and length class and these differences are most probably related to sexual differences in growth rate, natural mortality rate and energetic cost of reproduction. Red bandfish spawns over an extended period, from late spring to mid autumn, with larger females spawning earlier than smaller ones. Males reach maturity at a larger total length, 299 mm, and age, 2.6 years, than females, 219 mm and 1.9 years respectively, a fact most probably indicating the existence of social structure in red bandfish. Finally, red bandfish matures at a comparatively smaller length and age than other fish species.

Notes: Statistically significant regressions are presented between the maximum observed age, maximum gross weight, mean total length, mean gross weight, and mean weighted back-calculated total length at ages 3 and 4 years for red bandfish, Cepola macrophthalma, and the total nitrogen in three Aegean gulfs. In contrast, the regressions of all the above mentioned biological variables on phosphates in the three gulfs were not significant, a fact consistent with the view that nitrogen, as opposed to phosphorus, is the limiting factor in eastern Mediterranean marine ecosystems. After discussing possible genetic discontinuities between the three populations, being inferred from the paleoceanography of the study area, it is suggested that the three populations form a single gene pool expressing phenotypic plasticity shaped by the contrasting environmental conditions experienced.

Notes: The abundance-depth relationship, condition factor and feeding of red bandfish, Cepola macrophthalma, were studied from trawl samples collected seasonally in 1986–1988 in the western Aegean Sea (Greece). The red bandfish comprised numerically 1.4% of the total fish catch. Its abundance ranged between 0 and 1362 individuals/h (mean = 57.7 individuals/h, +s.d.= 124.7). The relationship between the natural logarithm of the mean number of individuals/h, ln[(n/h) + 1], and depth, D in m, was found to be described by the following quadratic model:〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00221112:JFB645:JFB_645_mu1"/〉 Feeding intensity and condition factor were significantly (P 〈0.05) lower in December and March, when annuli formation takes place, and significantly higher (〈0.05) in June and/or September when reproduction takes place. The red bandfish is a zooplankton predator. Copepods and euphausids dominated by far its diet and made up 60.4% and 31.1 % by number, respectively. The remainder of the diet was shared by cladocerans, decapods, mysids, chaetognaths, amphipods, fish larvae and decapod larvae. Red bandfish has probably evolved a zooplanktophagus habitat because, by providing a relatively abundant food supply, it will neither limit its high linear growth in the first 4–5 years of life nor increase its predatory induced mortality.

Notes: Age, growth and mortality of red bandfish, Cepola macrophrhalma (L.), from the western Aegean Sea were studied using the otoliths from 1113 fish and the length and weight of 3351 fish. Two regions were established (north and south of the Euripos Strait). The red bandfish grows allometrically (slope of length-weight regressions ≤2) and relatively rapidly until age 4 or 5 years. It is proposed that this rapid linear growth represents an adaptation which evolved to reduce the vulnerability of red bandfish to whole-fish swallowers. Back-calculated lengths-at-age showed significant differences between regions and between sexes. Males were larger than females after age 2 years. Maximum age of northern fish was also higher than southern fish (8 and 5 years respectively). Southern fish grow at a faster rate (K=0.379) but to a significantly smaller size (Lx=424.8mm t.l., Wx=25.1 g) than northern fish (K=0.214, Lx=676.1 mm t.l., Wx=90.9 g). Mortality rates (total and natural instantaneous mortalities) of southern fish were also higher than northern fish. We suggest that these variations represent responses to the different conditions of temperature and food availability prevailing in the two regions.

Notes: The feeding habits of the Lessepsian migrant Siganus luridus in the eastern Mediterranean (Kastellorhizo Isle, Dodecanese, Greece) are examined. The stomach contents of 209 specimens, 131–250 mm total length, collected by bottom trammel nets, April 1985 July 1986, were analysed. Feeding intensity was high, although it significantly declined during the spawning period in summer. Siganus luridus feeds on a diverse assemblage of benthonic algae including 24 genera (seven green, eight brown and nine red algae) contributing 84.4% by weight (green algae 3%, brown 70.3%, red 11 %). Posidonia oceanica, diatoms, hydrozoa and sand were also found in the stomachs examined. On an annual basis, Dictyota sp., Cysloseira sp., Sphacelaria sp., Gelidium sp., Dictyopteris membranacea, Kuckuckia spinosa and Padina pavonica predominated in the diet. Diet overlap, on a weight basis, indicated a similar food spectrum during spring and summer which was different from that in autumn.The high feeding intensity of S. luridus during the year (except for the spawning period), its nonselective euryphagous nature, its high competitive potential, and its position in the food web of the eastern Mediterranean ecosystem are important characteristics that, along with suitable oceanographic and ecological conditions for the development and survival of young stages, have enabled the successful establishment and build-up of the population of this Lessepsian migrant in its new environment. Possible competitive implications in the eastern Mediterranean ecosystem are also discussed.

Notes: In 18 marine fish species from the eastern Mediterranean, vertical mouth opening increased linearly with total length (LT) for 10 species and log-linearly for eight species. Horizontal mouth opening was linearly related to LT for 12 species and log-linearly for six species, whereas mouth area was a log-linear function of LT for all fish species examined. Mouth shape varied greatly covering the whole spectrum from a full circle to an extended oval. In addition, the trophic level of the 18 species could be expressed as an asymptotic function of mouth area. The results are discussed within the context of the trophic ecology of the species examined in the study area.

Notes: A 21-year record of monthly catches of Trachurus sp. (1964–1984, 252 observations) from the eastern Mediterranean (Greek waters) was analysed using (a) the Winters seasonal exponential smoothing method (WES), (b) the Auto Regressive Integrated Moving Averages (ARIMA) procedure and (c) the monthly averages corrected for linear trend method (MACLT). Fits for February 1966-December 1984 and forecasts for January 1985-December 1985 obtained by these methods were compared with actual catches during these periods and with those obtained from a simple “naive” method (NM), using as forecasts the monthly catches of the previous year. Fitting and forecasting performances were compared using 12 measures of accuracy. The results of the study indicated that ARIMA was far superior when compared with NM, MACLT and WES, and resulted in unbiased, accurate fits and forecasts, and in residuals which were essentially white noise. In addition, the measures used did indicate that MACLT was inferior in comparison to NM and WES. The potential use of WES in short-term fisheries forecasting is also discussed in the text.〈section xml:id="abs1-2"〉〈title type="main"〉ZusammenfassungKurzfristige Fischereivorhersagen: Vergleich der Angleichungs-, ARIMA-und RegressionstechnikenEine über 21 Jahre durchgeführte monatliche Fangstatistik von Trachurus sp. (1964–1984,254 Beobachtungen) aus dem östlichen Mittelmeer (Griechische Gewässer) wurde nach folgenden Methoden analysiert: (a) Winters saisonale, exponentiale Angleichung (WES); (b) Autoregressive integral-bewegte Mittelwerte (ARIMA); (c) monatliche Mittelwerte korrigiert nach der Methode der linearen Trends (MACLT). Anpassungen der Daten für den Zeitraum von Februar 1966 bis Dezember 1984 sowie Voraussagen für Januar bis Dezember 1985, die mit diesen Methoden erarbeitet wurden sind mil den aktuellen Fangdaten verglichen worden. In den Vergleich wurde weiterhin eine vereinfachte Methode („naive method”, NM) einbezogen, die die Fangdaten der jeweiligen Monate des Vorjahres nutzte. Für die Beurteilung der Anpassungsleistung und der Vorhersage wurden 12 Parameter verwendet. Die Ergebnisse dieser Studie belegen, daß die ARIMA-Methode den anderen Methoden (NM, MACLT und WES) in bezug auf Präzision der Anpassungen und der Vorhersagen sowie deren Abweichungen, die sich nur in der Größenordnung des Hintergrundrauschens bewegten, überlegen war. Weiterhin wurde auch deutlich, daß MACLT den Methoden NM und WES unterlegen war. Die potentielle Nutzung von WES für kurzfristige Fischereivorhersagen wird ebenfalls diskutiert.〈section xml:id="abs1-3"〉〈title type="main"〉RésuméPrediction è court-terme dans lespêcberies: Comparaison des techniques d'alignement, ARIMA et de régressionLes enregistrements de 21 années de prises mensuelles de Trachurus sp. (1964–1984, 252 observations) dans la Méditerranée orientale (eaux grecques) ont été analyses en utilisant a) la méthode d'alignement exponentiel saisonnier de Winters (WES), b) les moyennes flottantes intégrées autorégressiyes (ARIMA), c) les moyennes mensuelles corrigées par la méthode tendantielle linéaire (MACLT). L'aju-stement des données de février 1966 è décembre 1984 ainsi que les prévisions pour la période Janvier 85-décembre 85 obtenus par ces méthodes ont été compares avec les prises réelles pendant ces périodes et avec celles obtenues par une méthode naïve simple utilisant comme prévision les prises mensuelles de l'année précédente. Les performances des ajustements et des prévisions ont été comparés en utilisant 12 critères de précision. Les résultats de cette étude ont indiqués que la méthode ARIMA était de loin supérieure comparée avec la méthode naïve, MACLT et WES; et résultait dans des ajustements et previsions non biaisé et precis ainsi que dans des variations de l'ordre du bruit de fond: De plus, les

Notes: A total of 109 Greek aquaculture projects were approved by the EC Commission between 1987 and 1991 under Regulation 4028/86, of which 65 were for sea-bass/sea-bream and 24 for mussels. The total production capacity of these projects was 13,483 tonnes, 13,025,000 sea-bass/sea-bream fingerlings and 600,000 trout juveniles. The total expenditure for grants was 12.1 billions drachmas. The geographic distribution of the projects approved by both the EC Commission and the National Developmental Law 1262/1982 (incentives for investments in Greece) are discussed in the text. A cumulative employment figure for a total of 330 aquaculture approved/established projects in Greece is about 5,500 jobs, created m remote areas where there are few other sources of employment. Total aquaculture production (excluding lagoons) increased from 2,200 tonnes in 1980 to 7,550 tonnes in 1990. A trend model, fitted to the total 1980–1990 production, predicted 10,507 tonnes for 1992. The prospects of aquaculture in Greece as well as conflict with tourism and fishing are also discussed.

Notes: We present the relationships between total (TL), fork (FL) and standard (SL) length for 37 fish species and the relationships between TL and wet weight for 40 fish species from the Aegean Sea (Cyclades; Greece). The relationships between TL, FL and SL were all linear (for all cases: r2 〉 0.928). The values of the exponent b of the length–weight relationships ranged from 2.235 to 3.704.