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Spatial and temporal patterns in the Gulf of Alaska groundfish community in relation to the environment Item Type Thesis Authors Mueter, Franz Josef Download date 04/10/2021 00:30:01 Link to Item http://hdl.handle.net/11122/9539 INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. 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SPATIAL AND TEMPORAL PATTERNS IN THE GULF OF ALASKA GROUNDFISH COMMUNITY IN RELATION TO THE ENVIRONMENT A THESIS Presented to the Faculty of the University of Alaska Fairbanks in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY By Franz-Josef Mueter, M.S. Fairbanks, Alaska August 1999 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 9947762 UMI Microform 9947762 Copyright 1999, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SPATIAL AND TEMPORAL PATTERNS IN THE GULF OF ALASKA GROUNDFISH COMMUNITY IN RELATION TO THE ENVIRONMENT By Franz-Josef Mueter RECOMMENDED: Advisory Committee Chair Department Head APPROVED: R Dean, School of Fisheries and Ocean Sciences in of the Graduate School JF~(0 Date Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Abstract The GoA supports a rich demersal fish community dominated by gadids, pleuronectids, sablefish (Anoplopoma fimbria) and rockfishes (Sebastes spp.). This study describes the structure of the juvenile and adult groundfish communities of the Gulf of Alaska (GoA) in relation to their environment and along spatial and temporal gradients. Abundance data were obtained from trawl surveys of juvenile groundfishes in the nearshore areas of Kodiak Island (1991-1996), shrimp- trawl surveys in the same areas (1976-1995), and triennial bottom trawl surveys of adult groundfishes on the GoA shelf and upper slope (1984-1996). Species richness, species diversity, total abundance, and multivariate indices of species composition for each station sampled were statistically related to depth, temperature, salinity, sediment composition, geographic location, and time of sampling to identify spatial and temporal patterns in community structure. The observed patterns were then related to local and large-scale atmospheric and oceanographic trends. Both juvenile and adult groundfish communities were primarily structured along the depth gradient. The abundance of juvenile groundfishes decreased with depth from 0 to 100m, whereas the abundance of adults increased with depth to a peak at 150-200m. Species richness and diversity of the adult community had a significant peak at 200-300m. Spatial patterns suggested higher abundances, lower species richness and diversity, and a different species composition of demersal fishes in the western GoA compared to the eastern GoA. These large- scale spatial patterns appear to be related to differences in upwelling between the eastern and western GoA. A 40% increase in total groundfish biomass on the GoA shelf and upper slope was estimated between 1984 and 1996. Significant changes in species composition occurred in the nearshore areas of Kodiak Island in the early 1980s, from a community dominated by shrimp and small forage fishes to one dominated by large piscivorous gadids and flatfishes. The change in species composition in the nearshore community appeared to be linked to an increase in advection in the Alaska Current. Increased flow around the GoA may enhance the supply of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. nutrients and plankton on the shelf and upper slope, resulting in an increase in overall productivity of the pelagic and demersal biota. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V Table of Contents ABSTRACT--------------------------------------------------------------------------------------------------------m TABLE OF CONTENTS___________________________________________________________ V LIST OF FIGURES_____________________________________________________________ Vm LIST OF TABLES______________________________________________________________ XIII ACKNOWLEDGMENTS_________________________________________________________ XV CHAPTER 1: INTRODUCTION____________________________________________ 1 CHAPTER 2: THE GULF OF ALASKA_______________________________________________ 5 G e o l o g y ...................................................................................................................................................................... 5 H y d r o g r a p h y ...........................................................................................................................................................7 C lim a tic variability in t h e N o r t h e a s t P a c ific a n d its im p a c t o n t h e m a r in e ENVIRONMENT OF THE GULF OF ALASKA................................................................................................8 G r o u n d fish fish e r ie s in t h e G u l f o f A l a s k a .........................................................................................13 CHAPTER 3: METHODS____________________________________________ IS CHAPTER 4: LINKING COMMUNITY STRUCTURE OF SMALL DEMERSAL FISHES AROUND KODIAK ISLAND, ALASKA, TO ENVIRONMENTAL VARIABLES........................... 25 A b s t r a c t .................................................................................................................................................................. 25 Introduction ..........................................................................................................................................................26 M e t h o d s ....................................................................................................................................................................27 Sample collection and processing......................................................................................27 Environmental variables....................................................................................................29 Indices of community structure.......................................................................................... 30 Relating indices of community structure to environmental variables...................................33 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R e su l t s 34 Environmental variables....................................................................................................34 Relating indices of community structure to environmental variables...................................37 D is c u s s io n ................................................................................................................................................................53 A cknowledgments .............................................................................................................................................58 CHAPTER 5: CHANGES IN SPECIES COMPOSITION OF THE DEMERSAL FISH COMMUNITY IN NEARSHORE WATERS OF KODIAK ISLAND, ALASKA_______________ 59 A b s t r a c t .................................................................................................................................................................. 59 I ntroduction ......................................................................................................................................................... 59 M a t er ia ls a n d M e t h o d s ..................................................................................................................................61 R e s u l t s .....................................................................................................................................................................