Early Life History of Atlantic Mackerel (Scomber scombrus) in the Southern Gulf of St. Lawrence
| Autor: | T. C. Lambert, D. M. Ware |
|---|---|
| Rok vydání: | 1985 |
| Předmět: | |
| Zdroj: | Canadian Journal of Fisheries and Aquatic Sciences. 42:577-592 |
| ISSN: | 1205-7533 0706-652X |
| DOI: | 10.1139/f85-075 |
| Popis: | Results of a 4-yr study of the vertical distribution, development, and mortality of the early life history stages of Atlantic mackerel (Scomber scombrus) in St. Georges Bay, Nova Scotia, are summarized. Adult mackerel migrate to the southern Gulf of St. Lawrence and first appear in St. Georges Bay in the spring when the sea surface temperature is 7–8 °C. Peak spawning occurs about 26 d later, when the water temperature has warmed to 13 °C. Mackerel eggs tend to concentrate near the surface, particularly under light winds, and decline exponentially with depth. The rate of decline was a function of egg diameter and the temperature gradient in the top 5 m. During incubation, which lasts about 6 d, the median depth of the eggs increased at a rate of 1 m/d. This explains why recently hatched larvae were primarily between 5 and 10 m. As the larvae grew they moved progressively closer to the surface during the day; between the 3- to 8-mm stage the median depth decreased at a rate of 0.7 m/d. Mortality in the egg stage was of the order of 41%/d, and increased with respect to the annual rate of warming of the mixed layer. Larval mortality rates (corrected for net avoidance) were about 42%/d and were positively correlated with temperature. Although the mortality rate tended to be higher amongst first-feeding larvae, events during this stage did not change the rank order of abundance of the year classes — mortality was consistently high from fertilization to the 8-mm stage. There is some evidence in 1975, which was the warmest year, and the year with the highest larval mortality rate, that there was a poor spatial match between the size of mackerel larvae, at different depths, and the size of their planktonic food supply. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|