Commercial harvest of fish stocks and their appropriate management requires an understanding
of their population dynamics and of their ability to sustain exploitation.
Here, some ecological and evolutionary consequences of excessive exploitation are
examined.
In Chapter 2 I evaluate the knowledge base and status of commercially exploited
marine populations that undergo formal stock assessment. Despite a bias towards industrialised
countries and stocks of commercial importance, I show the pervasiveness
of overexploitation and, by using reference points of stock status, identify important
regional differences in the effectiveness of fisheries management.
In Chapter 3 I develop a data format suitable for ecological analyses to best disseminate
the valuable information contained in scientific trawl surveys. This data
format is suitable for inclusion into the public Ocean Biogeographic Information System
(OBIS) and provides detailed observations that are suitable to the reconstruction
of important fisheries-independent stock indices.
In Chapter 4 I examine the spatiotemporal dynamics of groundfish populations. A
positive abundance-occupancy relationship was estimated for the majority of groundfish
populations examined suggesting that this well-described terrestrial pattern is
also pervasive in the marine environment. Spatial hysteresis was exhibited by numerous
populations, indicating that the spatial distribution of individuals failed to
recover despite recoveries in abundance.
In Chapter 5 I estimate the demographic consequences of changes in growth and
maturation characteristics. The ability of a population to sustain harvest, and its
ability to recover from previous depletions can be overestimated because of trends
towards earlier maturation and slower growth.
In Chapter 6 I conclude the thesis by discussing the implications of my research to
fisheries science and management. I argue that trends in the spatial distribution and
the overall productivity of populations must be accounted for when determining sustainable
fishing levels and when predicting recovery trajectories under various catch
abatement scenarios. While successful management measures have been implemented
in a number of marine ecosystems, this thesis highlights the importance of improving
our capacity to understand the dynamics of exploited populations and to fully use
the wealth of available monitoring and assessment data.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/15069 |
| Date | 25 May 2012 |
| Creators | Ricard, Daniel |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
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