Temporal and spatial variation in community diversity, richness and abundance of ichthyoplankton in coastal Newfoundland over two decades

Carter-Lynn, Kelly P. (Kelly Patricia). (2009) Temporal and spatial variation in community diversity, richness and abundance of ichthyoplankton in coastal Newfoundland over two decades. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (8MB)

Abstract

I examine the patterns of variation in the larval fish community from coastal Newfoundland using data from 68 surveys conducted during the summer months between 1982 and 2002. I review the literature concerning changes in the adult fish community that have taken place, and then review the hypotheses about their possible causes. The principle debate surrounding the collapse of the Newfoundland groundfish deals with the relative roles of fishing pressure versus the potential influence of seawater temperature during the years following peak fishing pressure in the 1960's. I address whether differences in gear type (Bongo vs. Ring nets) might affect my ability to detect changes in the larval fish community as a result of selection loss or avoidance. Based on the results of statistical comparisons and on calculated catch ratios of < 1.61 concluded that no consistent bias was present as a result of gear type and that the abundance data in this study are sufficiently comparable for use in larger temporal studies. I then contrast temporal changes in the larval community of three bays. Based on Multidimensional Scaling plots, Group Average Cluster Analysis and species abundance plots, I concluded that temperature (seasonal structure) plays a role in determining community composition of the larval fish studied, producing distinct larval assemblages at specific times of the year. I also concluded that below average water temperatures during the early 1990's affected the community composition of the larva; as cold-water species were unusually present during summer months. Additionally Analysis of Similarity showed that larval species abundance significantly decreased post 1992 and some non-commercial species showed smaller declines in abundance than those commercially targeted. Finally, I examine the scale at which these changes have occurred, to determine whether large-scale temporal changes occur in species diversity or dominance, and whether changes correlate within and among the bays surrounding Newfoundland's Avalon Peninsula. Larval fish abundance displayed significant changes during the same time periods in all the bays examined in this study. However, further investigation is needed before conclusions can be made regarding how species composition differs in the bays surrounding the Avalon Peninsula.

Actions (login required)

View Item