Temperature and the distribution of mature female lobsters (Homarus americanus Milne Edwards) off Canso, Nova Scotia.
Date
1995
Authors
Ugarte, Raul Alejandro.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
A study on the reproductive ecology of mature females lobsters (Homarus americanus, Milne Edwards) was carried out on Canso N. S. lobster grounds during 1991 and 1992. These waters are cold with six months at $10\sp\circ$C. During the summer prevailing southwest winds produce upwelling events of variable intensity, which can drop surface temperatures to as low as 5$\sp\circ$C. These events co-occur with important phases of lobster reproduction such as embryo maturation and hatching, larval development, adult molting and mating, ovary development and egg extrusion. In addition to the thermal instability of the warm water period, the Canso lobster ground has a highly variable bottom topography creating a range of habitats and thermal regimes over short distances.
Surveys made with the help of commercial fishermen showed that during late spring/early summer, mature females are not homogeneously distributed over the grounds, but associated with certain physical features and warm shallow waters. A tag/recapture study showed that females with maturing ovaries and embryos move rapidly in mid- to late spring to the shallows ($<$10 m). Using the Perkins Eye Index and cement gland techniques on animals from the commercial survey, from the tag/recapture study and on animals caged at depth (3 m to 17 m) it was shown that the warm shallow waters accelerate both ovary and embryo maturation. The time available in a typical year to complete the reproductive and early recruitment processes is brief, thus this spring short-term movement reduces the risk of a year-class failure. The study's results are then used to model life history distribution in relation to spatial and temporal steady state variables, and to add new insights into the Canso Causeway closure and the collapse of the eastern shore lobster fishery during the 1970s.
Thesis (Ph.D.)--Dalhousie University (Canada), 1995.
Surveys made with the help of commercial fishermen showed that during late spring/early summer, mature females are not homogeneously distributed over the grounds, but associated with certain physical features and warm shallow waters. A tag/recapture study showed that females with maturing ovaries and embryos move rapidly in mid- to late spring to the shallows ($<$10 m). Using the Perkins Eye Index and cement gland techniques on animals from the commercial survey, from the tag/recapture study and on animals caged at depth (3 m to 17 m) it was shown that the warm shallow waters accelerate both ovary and embryo maturation. The time available in a typical year to complete the reproductive and early recruitment processes is brief, thus this spring short-term movement reduces the risk of a year-class failure. The study's results are then used to model life history distribution in relation to spatial and temporal steady state variables, and to add new insights into the Canso Causeway closure and the collapse of the eastern shore lobster fishery during the 1970s.
Thesis (Ph.D.)--Dalhousie University (Canada), 1995.
Keywords
Biology, Ecology., Biology, Oceanography., Biology, Zoology.