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Notes: Twenty-two salmon smolts, Salmo salar L., carrying miniature sonic tags were tracked individually for periods of up to 175 h in Loch Voil, Scotland, during May 1979 and 1980. Activity was predominantly nocturnal, 80% occurring between 21.00 and 06.00 hours, and was apparently undirected. Average velocities during this active interval were 0.6 body lengths per second (bl s−1), with 98 and 93% of the time spent moving at less than 2 and less than 1 bl s−1, respectively. The rates of downstream displacement were 0.04 bl s−1 in 1979 and 0.01 bl s−1 in 1980. The direction of displacement of smolts and of movement of water at a depth of 1 m was positively correlated (P〈0.001) and smolt displacement was biassed slightly ahead of water movement. Mean step lengths were 141 and 200 m in 1979 and 1980, respectively. Rates of downstream passage of 327 ICES plate-tagged smolts released 16.8 km upstream of the fish trap at Clunie dam, Loch Tummel, during the spring migrations of 1975 and 1976 averaged 0.13 bl s−1 in each year: net surface water movement was about 3.7 times this rate during the same intervals. These data are consistent with the model of passive smolt migration postulated by Tytler et al. (1978) and suggest that the active component required to ensure passage through a loch (Thorpe & Morgan, 1978) is very small.

Notes: Truss and length measurements were made on 463 tilapia Oreochromis niloticus of known mass. These measurements were then used to build mathematical models to estimate tilapia biomass. Two different approaches were used to build the models. The first was to take some simple mathematical models, and to optimize them using least squares regression. The second approach was to build models using artificial neural network software. Models were built for two different but overlapping size ranges and both approaches were successful in creating models that estimated the total biomass to within ±1%. The truss measurements were also used to assess the principal shape components of different sized tilapia.

Notes: The reroductive biology and growth of the Central American cichlid, Cichlasoma urophthalmus, was studieg in a brackish water lagoon in Celestun, Yucatan, Mexico, between spring 1985 and spring 1986. The fish is strongly euryhaline and reproduces in brackish waters as well as in fresh water, having clear thermophilic habits, and resisting low oxygen levels. The population in the lagoon is constituted by fast growing fish which have one, or exceptionally two, reroductive seasons in their lifetimes. The mean standard length of catured fish was 134.7 mm for mais and 135.3 mm for females but no significant difference was found getween them. A significant difference in the sex ratio was found between summer and autumn, presumably due to the type of parental care exhibited by this species. Examination of ovaries showed that the reproductive season starts in mid-April and extends until mid-November, with reproductive peaks in sprin and summer. The fecundity ranged from 2085 to 6615 ova/female. The minimum size of maturity of females was 102 mm (50 g). Specific attributes of this species are compared with those of some African cichlids and are discussed in terms of aquaculture.〈section xml:id="abs1-2"〉〈title type="main"〉Zusammenfassung Die Reproduktionsbiologie und das Wachstum des zentralamerikanischen Cichliden Cichlasoma urophthalmus (Günther)Die Reproduktionsbiologie und das Wachstum des zentralamerikanischen Cihliden Cichlasoma urophthalmus wurden in einer Brackwasserlagune in Celestun, Yucatan, Mexiko untersucht. Diese Arbeiten fanden im Zeitraum zwischen dem Frühjahr 1985 und Frühjahr 1986 start. Diese stark euryhaline Fischart vermehrt sich sowohl in Brack- als auch in Säßwasser, wobei thermophile Eigenschaften sowie eine deutliche Widerstandsfähigkeit gegen niedrige Sauerstoffgehalte des Wassers beobachtet wurden. Die Population, die in der Lagune lebte, bestand aus schnell wachsenden Individuen, die sich ein oder maximal zweimal während ihres Lebenszyklus vermehren. Die mittlere Standardlänge der gefangenen Tiere betrug 134,7 mm für die Männchen, sowie 135,3 mm für die Weibchen, die Unterschiede der mittleren Länge waren nicht signifikant. Ein signifikanter Unterschied bestand zwischen dem Verhältnis von Männchen zu Weibchen im Sommer und Herbst, was wahrscheinlich auf die Art vom Brutpflegeverhalten dieser Art zurückzuführen ist. Untersuchungen der Ovarien zeigten, daß die Reproduktion gegen Mitte April einsetzt und bis Mitte November andauert. Die Höhepunkte in der Vermehrung liegen im Frühjahr und Sommer. Die Fruchtbarkeit schwankte zwischen 2085 und 6615 Eiern pro Weibchen. Die Mindestgröße der Weibchen urn die Geschlechtsreife zu erlangen betrug 102 mm (50 g). Spezifische Eigenschaften dieser Fischart werden mit denen afrikanischer Cichliden verglichen und unter aquakulturtechnischen Gesichtspunkten diskutiert.

Notes: The optimum growth, food intake, food conversion efficiency, final body composition and mortality of juvenile Cichlasoma urophthalmus (Günther) was studied at different temperatures, ranging from 22.5 to 36.3°C. The results showed that food intake and specific growth rate increase rising to an apparent optimum at about 33.1°C. Multiple regression equations were derived which can be used to predict food intake and specific growth rate when temperature and initial body weight are known.

Notes: The salinity tolerance of Cichlasoma synspilum (Hubbs) fry was measured at intervals up to 144 h. Good survival was obtained only up to about 5%o, and 100% mortality was recorded after 4 h at 20%o. The 144-h LC50 was estimated to be 14.5%o and this species is clearly a very stenohaline, freshwater animal. Respiratory rates of animals from 0.8 to 245 g were measured in fresh water at temperatures of 20,25, 30 and 35 C. The rates were similar to those in other cichlids, but were notably lower than those recorded for Cichlasoma urophthalmus (Günther). This species has potential for aquaculture in fresh water and marginal brackish waters within its natural range, and the experiments reported here provide useful background data for system design and husbandry.

Notes: Abstract. The effectiveness of xylocaine anaesthesia, potentiated with sodium bicarbonate, was investigated on the altiplano cyprinid, Algansea lacustris Steindachner. The drug gave excellent sedation, handling and recovery and was effective at doses between 50 and 300 mg/l in 1 g/l sodium bicarbonate.

Notes: Abstract. The morphometric relationships, standard length-weight, standard length-width and weight-width for Cichlasoma urophthalmus (Günther) in the weight range 0.78-262g were: log10 weight =−4.35 + 2.95 × (log10 standard length); log10 width =−0.73 + 0 99 × (log10 Standard length) and log10 width = 0.74 + 0.33 × (log10, weight). Two box graders were designed and tested based on these data. The operation efficiency (expressed as a percentage of the sample used to test it) was 96.1 % and 95% for the two graders. Results indicated a tendency to undergrading (small fish detained by the bars) by the first grader and overgrading (large fish going between the bars) by the second, the latter as a result of the major variability in the body shape from fish as they grow. The results are satisfactory, and larger graders for commercial use could be constructed based on these relationships.

Notes: Native species development is often based upon the interests of individuals, the specialities of particular institutions or even the simplicity of the technology required. The methodology of developing native species for aquaculture is discussed with particular reference to current concerns over loss of biodiversity. The biological and technical issues are outlined and prioritized, and the question of socio-economic targeting of the activity, the needs for marketing and promotion, and the requirements for farming systems studies are described. Time-scales and costs for research and development programmes are illustrated using the example of Cichlasoma urophthalmus (Günther) culture in Mexico. Finally, the increasing use of geographical information systems large-scale strategic planning and in facility location is also discussed.