60
M.O. White
It is likely that the maintenance of larvae in retention zones is very
important to the survival of species with a protracted pelagic phase in
their early life-history. It has been shown that wind-sheer has an
important effect on fine-scale oceanographic features because at speeds
above a critical wind velocity the lee gyre is disrupted and eddies detach,
and with them parcels of neritic water and the entrained plankton are
advected away from the island shelf [23]. Therefore the maintenance and
longevity of the shelf-break front and near shelf gyres will have a major
influence on the success or failure of recruitment in any given season
and may be a primary forcing factor resulting in the large inter-annual
variations in larval abundance. This process will influence the
recruitment and demography of fish populations at all the peri-Antarctic
islands because of the importance of retaining pelagic larvae in suitable
habitats to complete their development and recruitment to the juvenile
phase in their early life-history.
The combination of intermittent recruitment due to physical factors as
described above, competition with species that have shorter life cycles
and faster growth rates, and by-catch effects, are likely to be factors
delaying the re-establishment of fish stocks depleted by commercialscale fishing.
Consequences for Genetic Exchange and Affinities
Many life-history characteristics among Antarctic fish will influence the
exchange of genetic information. Gene-flow is likely to be restricted by:
geographical isolation of populations, the dependence of shelf habitats,
delayed maturation, low fecundity, annual spawning, and the potential
losses of pelagic eggs and larvae by advection. On the other hand, geneflow will be promoted by: the protracted development of eggs, larvae
and juveniles, prolonged development in pelagic habitats as well as the
longevity and eurybathyal distribution of adults. The balance between
the factors restricting and promoting dispersal will be important in
determining the levels of genetics exchange between populations of
Antarctic fish.
Studies on the genetic affinities among species with wide but disjunct
distributions and the distribution of pelagic early life history stages need
to be addressed to progress an understanding of the population dynamics
and associations of Antarctic fish. The dependence and duration within
pelagic habitats during each stage of a species life-history will have
fundamental implications for resolving such questions as genetic
exchange, stock identity and species affinity among Antarctic fish.
M.O. White
It is likely that the maintenance of larvae in retention zones is very
important to the survival of species with a protracted pelagic phase in
their early life-history. It has been shown that wind-sheer has an
important effect on fine-scale oceanographic features because at speeds
above a critical wind velocity the lee gyre is disrupted and eddies detach,
and with them parcels of neritic water and the entrained plankton are
advected away from the island shelf [23]. Therefore the maintenance and
longevity of the shelf-break front and near shelf gyres will have a major
influence on the success or failure of recruitment in any given season
and may be a primary forcing factor resulting in the large inter-annual
variations in larval abundance. This process will influence the
recruitment and demography of fish populations at all the peri-Antarctic
islands because of the importance of retaining pelagic larvae in suitable
habitats to complete their development and recruitment to the juvenile
phase in their early life-history.
The combination of intermittent recruitment due to physical factors as
described above, competition with species that have shorter life cycles
and faster growth rates, and by-catch effects, are likely to be factors
delaying the re-establishment of fish stocks depleted by commercialscale fishing.
Consequences for Genetic Exchange and Affinities
Many life-history characteristics among Antarctic fish will influence the
exchange of genetic information. Gene-flow is likely to be restricted by:
geographical isolation of populations, the dependence of shelf habitats,
delayed maturation, low fecundity, annual spawning, and the potential
losses of pelagic eggs and larvae by advection. On the other hand, geneflow will be promoted by: the protracted development of eggs, larvae
and juveniles, prolonged development in pelagic habitats as well as the
longevity and eurybathyal distribution of adults. The balance between
the factors restricting and promoting dispersal will be important in
determining the levels of genetics exchange between populations of
Antarctic fish.
Studies on the genetic affinities among species with wide but disjunct
distributions and the distribution of pelagic early life history stages need
to be addressed to progress an understanding of the population dynamics
and associations of Antarctic fish. The dependence and duration within
pelagic habitats during each stage of a species life-history will have
fundamental implications for resolving such questions as genetic
exchange, stock identity and species affinity among Antarctic fish.