Effect of temperature on hatching and growth of cuban gar (Atractosteus tristoechus) larvae
Hatching success, growth, development and survival of Cuban gar ( Atractosteus tristoechus ) larvae were examined at different temperatures (26, 28 and 30 o C) up to 18 days after hatching (DAH). The time to hatching was inversely related to the incubation temperature (87, 100 and 111 h). Larval survival at the time of hatching was significantly lower at 30 o C (50.3 %), coinciding with the highest larval mortality (30.2 %). Growth rates were 1.75 mmd -1 -10.4 % d -1 at 26 o C,1.30 mm d -1 -10.2 % d -1 -1 at 28 o C and 1.40 mm d -1 -10 % d -1 at 30 o C. Three similar critical periods were identified: 0-6, 7-11 and 12-18 DAH. During the first period, a similar increase in weight and a significant increase in total length occurred, mainly at 30 o C, indicating a more efficient reconversion of the yolk reserves. Later, growth was equally slow, corresponding with the transitional period from endogenous to exogenous feeding, indicating a similar physiologic pattern regardless of incubation temperature. Weight and length increased during the last period, with the greatest increase at 26 o C in contrast with the lowest gain at 30 o C. The inflexion points of many morphometric characters and the developmental stages accelerated with the increasing temperature. Although it was impossible to determine the optimal temperature, it was evident that 26 o C favored hatching success and larval growth.
Effects of Temperature on Growth and Efficiency of Yolk Utilisation in Eggs and Pre-feeding Larval Stages of Atlantic Salmon
Three embryonic stages of Atlantic salmon (Salmo salar L.) were subjected to eight constant incubation temperatures (4, 7, 10, 12, 14, 16, 19 and 22 °C) exceeding the range usually experienced in natural conditions. A change in thermal tolerance during the embryonic and larval development was registered: pre-hatching stages showed an upper thermal limit at about 16 °C, while hatched larvae survived until 22 °C. Temperature significantly affects developmental rate, resulting in a faster development and, consequently, lower yolk weight percentage at higher temperatures. We found positive relationships between incubation temperature and body size (length and weight) in the less developed stages, in which some yolk remained, but size decreased at increasing temperatures when yolk was completely exhausted.
The smolt run and postsmolt survival of Atlantic salmon, Salmo salar L., in relation to early summer water temperatures in the northern Baltic Sea
–  The timing of the smolt migration of Atlantic salmon, Salmo salar L., was investigated during 1972–2002 in the Simojoki, a river flowing into the northern Baltic Sea. The onset of the smolt run was positively correlated with the river water temperature; a rise in water temperature above 10 °C being the main proximate environmental triggering factor. There was also a weaker correlation between the decreasing river discharge in the spring and the onset of the smolt migration. The duration of the main run was shorter in the years when the onset of the smolt run was delayed. No differences were found in the onset timing or in the duration of the smolt run between wild smolts and semi-wild smolts released into the river as parr. A polynomial equation fitted to the annual data on the survival of Carlin-tagged wild smolts and the sea surface temperature (SST) in June off the river mouth appeared to follow a dome-shaped pattern. Survival was lower in cold early summers (SST <9 °C) than in those with an average SST (9–11.9 °C), and lower again, although not significantly, in warm early summers (SST ≥12 °C). Too low and probably also too a high water temperature in early summer could thus be one of the underlying reasons for the fluctuations observed in postsmolt survival in the Baltic Sea. 
 
Resumen 
 
1. Desde el ano 1972 hasta el ano 2002, investigamos el periodo de migracion de los ‘smolts’ de Salmo salar del rio Simojoki, un rio que fluye hacia el norte del Mar Baltico (Finlandia). Para ello, capturamos ‘smolts’ con trampas en la desembocadura del rio y colectamos datos ambientales tanto del rio como de la zona de estuario. 
 
 
 
2. El inicio de la migracion estuvo positivamente correlacionado con la temperatura del agua, siendo una elevacion de 10 °C el factor ambiental inmediato causante de la migracion. Detectamos tambien una correlacion menor entre el inicio de la migracion y el declive primaveral del caudal del rio. La duracion de la migracion fue menor en los anos en los que se retraso el inicio de la migracion. 
 
 
 
3. No aparecieron diferencias ni en el inicio ni en la duracion de la migracion entre ‘smolts’ naturales y semi-naturales repoblados en el rio como juveniles debido probablemente a su pertenencia a una fase juvenil similar. La supervivencia de ‘smolts’ naturales fue estudiada con marcas tipo ‘Carlin’ y consideramos que la tasas de recaptura de marcas fueron un reflejo del exito de los peces marcados despues de la mortalidad natural. 
 
 
 
4. Una ecuacion polinomial ajustada a los datos anuales de supervivencia de ‘smolts’ naturales marcados contra la temperatura de la superficie marina (SST) fuera del rio en Junio, describio un patron con forma de domo. La supervivencia fue menor en los veranos cuyo inicio fue mas frio (SST <9 °C) que en los veranos con temperaturas intermedias (SST = 9–11.9 °C) e inferiores a su vez, aunque no significativamente, en los veranos cuyo inicio fue mas caluroso (SST ≥12 °C). Asi, temperaturas muy bajas o muy altas durante el inicio del verano pueden ser el factor que subyace a las fluctuaciones observadas en la supervivencia de individuos ‘postsmolt’ del Mar Baltico.