| dc.contributor.author | Muelbert, Jose Henrique. | en_US |
| dc.date.accessioned | 2014-10-21T12:36:12Z | |
| dc.date.available | 1994 | |
| dc.date.issued | 1994 | en_US |
| dc.identifier.other | AAINN93830 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55427 | |
| dc.description | Despite the economic importance of herring fisheries and several years of intensive research, proximate causes for variability in the recruitment of herring remain unclear. In this thesis, the feeding environment of herring larvae from the coastal waters off southwest Nova Scotia is evaluated and discussed in the light of current hypotheses that attempt to explain variable survival during the early life history of pelagic fish. | en_US |
| dc.description | Throughout the North Atlantic, fall-spawned herring larvae predominantly inhabit coastal regions with tidally well mixed waters. Data from two cruises confirm that large aggregations are confined to well mixed waters off SW Nova Scotia. Physical-behavioural interactions could contribute to this pattern. The diel periodicity of vertical migration exhibited by the larvae, however, is not sufficient to explain the maintenance of their horizontal position through interaction with semi-diurnal tidal current. Alternatively, lower prey abundance in stratified waters could lead to increased mortality from starvation and account for the observed spatial distribution of the larvae. Results show that larvae in well mixed and stratified regions off SW Nova Scotia were exposed to similar concentrations of microzooplankton. Thus, variation in food concentration alone is not sufficient to explain the maintenance of the aggregations in the well mixed region. | en_US |
| dc.description | It has frequently been suggested that relative motions of predator and prey influence the feeding rate of planktonic organisms. Dimensional analysis of relevant biological parameters describing herring life history and field data shows that tidally well mixed regions constitute a preferential feeding environment for herring larvae because turbulence enhances predator-prey encounter rates. Hence, feeding rates should be greater in well mixed regions as compared to stratified regions with similar food abundance. Indeed, measurements of RNA/DNA ratios indicate that larvae from the well mixed areas were healthier than those from stratified areas, and had similar condition throughout the water column. However, larvae from both regions were generally in good condition, supporting the initial finding that during the fall, food is adequate for larval growth throughout the coastal zone. | en_US |
| dc.description | This thesis supports the hypothesis that tidal mixing enhances the feeding environment of herring larvae. Furthermore, it indicates that as food availability decreases towards the winter, larvae in stratified waters may be more susceptible to starvation. Therefore, differential mortality between the two regions may be the proximate cause for the apparent retention of larvae during winter in the well mixed waters off southwest Nova Scotia. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1994. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Oceanography. | en_US |
| dc.subject | Agriculture, Fisheries and Aquaculture. | en_US |
| dc.title | The relevance of feeding environment to "retention" of Atlantic herring (Clupea harengus) larvae. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
