Environmental Factors Influencing the Distribution of Juvenile Groundfish in Nearshore Habitats of Southwest Nova Scotia

1989 ◽  
Vol 46 (8) ◽  
pp. 1277-1286 ◽  
Author(s):  
John K. Horne ◽  
Steven E. Campana
Keyword(s):  
Physical Environment ◽  
Environmental Variables ◽  
Gadus Morhua ◽  
Detrended Correspondence Analysis ◽  
Stepwise Multiple Regression ◽  
Otter Trawl ◽  
Pseudopleuronectes Americanus ◽  
Marine Habitats ◽  
Components Analysis ◽  
Ordination Diagram

Eight nearshore (< 20 m) marine habitats were surveyed to estimate the relative abundance of juvenile groundfish and to assess the environmental variables influencing their distribution. Surveys were conducted as part of a depth-stratified, random sampling design; at each site a small otter trawl was towed for 15 min at eight stations in each of three depth strata. A suite of 13 environmental variables were measured in association with each tow. A total of 1908 fish from 13 different species were caught at 191 completed trawl stations. Standardized centered principal components analysis, orthogonally rotated factor analysis, and detrended correspondence analysis (DCA) were used to delineate aggregations in the abundance data. DCA coupled with stepwise multiple regression best resolved the species' distributions and dominant gradients in the environment. The first two DCA axes reflected estuarine to coastal gradients (68% of the variance) and significant environmental variables were plotted as vectors in the ordination diagram. An estuarine assemblage of species, characterized by winter flounder (Pseudopleuronectes americanus) and white hake (Urophycis tenuis), was associated with waters that were warmer, less saline, more turbid, and overlying a finer grained substrate, than a coastal assemblage of species which included cod (Gadus morhua) and rock gunnel (Pholis gunnellus). The biologically significant gradients corresponded to those which dominated variation in the physical environment.

Influence of climatic changes on the parasites of Atlantic cod Gadus morhua off coastal Labrador, Canada

2006 ◽  
Vol 80 (2) ◽  
pp. 193-197 ◽  
Author(s):  
R.A. Khan ◽  
C.V. Chandra
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Age Groups ◽  
Climatic Conditions ◽  
Otter Trawl ◽  
Commercial Fishery ◽  
Metazoan Parasites ◽  
Mean Values ◽  
The North

AbstractA study was conducted in 2000 and 2003, following the collapse of the commercial fishery in 1990, to compare metazoan parasites of Atlantic cod Gadus morhua, captured off coastal Labrador, with samples taken in 1980 and 1986. Fish were captured by otter trawl offshore in the North Atlantic Fish Organisation subarea 2J. Parasites were removed from the digestive tract, stained, identified and compared between the different groups. Both the prevalence and mean abundance of trematodes, larval nematodes and E. gadi were significantly lower in fish taken in 2000 and 2003 than in 1980. While mean values of trematodes and nematodes declined in 1986, those of Echinorhynchus gadi remained unchanged in 1986 and 1990. Four-year-old cod sampled in 1990 harboured significantly fewer E. gadi than older age groups. The most commonly occurring trematodes included Podocotylereflexa, Lepidapedon elongatum, Derogenes varicus and Hemiurus levinseni while the larval nematode, Anisakis sp. was predominant. Comparison of offshore samples taken in 2000 and 2003 with others taken in previous years suggests an overall decline of parasites coincident with a change in climatic conditions, the absence of a major food source, namely capelin Mallotus villosus, of cod and ultimately the decline of the Labrador population.

scholarly journals Non-linearity in stock–recruitment relationships of Atlantic cod: insights from a multi-model approach

2019 ◽  
Vol 77 (4) ◽  
pp. 1492-1502 ◽  
Author(s):  
Camilla Sguotti ◽  
Saskia A Otto ◽  
Xochitl Cormon ◽  
Karl M Werner ◽  
Ethan Deyle ◽  
...  
Keyword(s):  
Environmental Variables ◽  
Gadus Morhua ◽  
Fishery Management ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Fish Stock ◽  
Recovery Potential ◽  
Stock Recruitment ◽  
Model Approach ◽  
Non Parametric

Abstract The stock–recruitment relationship is the basis of any stock prediction and thus fundamental for fishery management. Traditional parametric stock–recruitment models often poorly fit empirical data, nevertheless they are still the rule in fish stock assessment procedures. We here apply a multi-model approach to predict recruitment of 20 Atlantic cod (Gadus morhua) stocks as a function of adult biomass and environmental variables. We compare the traditional Ricker model with two non-parametric approaches: (i) the stochastic cusp model from catastrophe theory and (ii) multivariate simplex projections, based on attractor state-space reconstruction. We show that the performance of each model is contingent on the historical dynamics of individual stocks, and that stocks which experienced abrupt and state-dependent dynamics are best modelled using non-parametric approaches. These dynamics are pervasive in Western stocks highlighting a geographical distinction between cod stocks, which have implications for their recovery potential. Furthermore, the addition of environmental variables always improved the models’ predictive power indicating that they should be considered in stock assessment and management routines. Using our multi-model approach, we demonstrate that we should be more flexible when modelling recruitment and tailor our approaches to the dynamical properties of each individual stock.

The leech as a vector of a fish piroplasm

1980 ◽  
Vol 58 (9) ◽  
pp. 1631-1637 ◽  
Author(s):  
R. A. Khan
Keyword(s):  
Marine Fish ◽  
Blood Meal ◽  
Gadus Morhua ◽  
Infected Fish ◽  
Binary Fission ◽  
Gut Contents ◽  
Pseudopleuronectes Americanus ◽  
Infected Blood ◽  
Fish Blood ◽  
Anarhichas Lupus

A piroplasm, Haemohormidium beckeri, is redescribed from two marine fish, Lycodes lavalaei and Lycodes vahlii (Zoarcidae). The parasite divided by both binary fission and schizogony. In the latter process, up to eight merozoites were produced and these developed within mature erythrocytes. Infections were prevalent among fish from areas off the Labrador coast. Parasitemias, which varied from light infections to estimates of 60 parasites/1000 erythrocytes, were recorded in 15 fish for about 6 months. Subinoculation of infected blood initiated infections in two perciform fish, Myoxocephalus octodecemspinosus and Anarhichas lupus, but not in a pleuronectiform, Pseudopleuronectes americanus, or a gadiform, Gadus morhua. Natural infections were present in three leeches, Platybdella olriki, that had fed on an infected L. lavalaei. Piroplasms were also observed in the gastrointestinal content of all 94 laboratory-reared leeches, Johanssonia arctica, dissected 7 through 109 days after engorgement on infected fish blood. Inoculations of gut contents from leeches after digestion of a blood meal produced infections in uninfected fish. Natural transmission occurred when leeches were fed again on susceptible fish, whereas pipetting entire leeches into the stomach of fish did not initiate infections. This is the first evidence that leeches transmit piroplasms in nature to fish.

Patterns of behavior in the Texas tortoise, Gopherus berlandieri: a multivariate ordination approach

2001 ◽  
Vol 79 (8) ◽  
pp. 1363-1371 ◽  
Author(s):  
Richard T Kazmaier ◽  
Eric C Hellgren ◽  
David R Synatzske
Keyword(s):  
Correspondence Analysis ◽  
Wildlife Management ◽  
Environmental Variables ◽  
Detrended Correspondence Analysis ◽  
Behavioral Variability ◽  
Significant Variable ◽  
Active Behavior ◽  
Management Area ◽  
Dry Conditions ◽  
Patterns Of Behavior

We compared the distribution of 19 categories of behavior exhibited by 47 adult Texas tortoises (Gopherus berlandieri) over 3 years with the use of detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA). DCA revealed a gradient from passive to active behavior along axis 1. Tortoises were more active in 1994 and less active in 1996. This pattern was likely due to the extremely hot and dry conditions in 1996. Year was the most significant variable explaining variability in behavior when sex, age, size, year, and grazing treatment (pastures grazed versus ungrazed by cattle) were used as environmental variables in CCA. Age, size, and grazing treatment were not significant variables in CCA. Tortoises used proportionally more burrows, shallow surface depressions termed pallets, and cavity pallets, and ate more cactus in 1996. More foraging and active behaviors, like courtship, were observed in 1994. Sex was a significant variable in explaining behavioral variability after the effects of year were controlled for. Males tended to exhibit more active behaviors than females. Our analyses suggested that the grazing regime used in Chaparral Wildlife Management Area did not affect the patterns of behavior exhibited by this protected tortoise.

Influence of the choice of physical and chemistry variables on interpreting patterns of sediment contaminants and their relationships with estuarine macrobenthic communities

2010 ◽  
Vol 61 (10) ◽  
pp. 1109 ◽  
Author(s):  
Anthony A. Chariton ◽  
Anthony C. Roach ◽  
Stuart L. Simpson ◽  
Graeme E. Batley
Keyword(s):  
Environmental Variables ◽  
Data Extraction ◽  
Extraction Procedure ◽  
Primary Objective ◽  
Metal Extraction ◽  
Acid Volatile Sulfide ◽  
Macrobenthic Assemblages ◽  
Sediment Contaminants ◽  
Components Analysis ◽  
Iron And Manganese

A primary objective of contaminated sediment risk assessments is to identify if contaminant enrichment is eliciting an ecological response. Using complementary environmental and biotic datasets, we examined five scenarios with respect to: dataset complexity; metal extraction; normalisation of organics; the inclusion/exclusion of acid-volatile sulfide data, and iron and manganese concentrations. Spatial distributions of abiotic variables were examined by principal components analysis, with canonical correspondence analysis used to examine the total and partitioning of biological variation. Metals were the dominant contaminant and explained the largest proportion of variation in the macrobenthic data. Extraction procedure and carbon normalisation of organics had little influence on the overall analysis. Porewater metal data was essential for interpretation, with excess of acid-volatile sulfide over simultaneously extractable metals being a poor surrogate. In the canonical correspondence analyses, the inclusion of Fe/Mn accentuated the covariation between the ecological and contaminant variables. Multimodel comparisons aided interpretation by emphasising specific relationships among environmental variables and their interactions with the biotic data. Furthermore, for future examinations of the described system, the findings can be used to reduce the collection of redundant environmental variables or variables that are poorly correlated with changes in macrobenthic assemblages.

scholarly journals Food Resource Utilization by Five Species of Benthic Feeding Fish in Passamaquoddy Bay, New Brunswick

1986 ◽  
Vol 43 (8) ◽  
pp. 1534-1546 ◽  
Author(s):  
J. Stevenson Macdonald ◽  
Roger H. Green
Keyword(s):  
Fish Species ◽  
Gadus Morhua ◽  
Function Analysis ◽  
Food Resource ◽  
Stomach Contents ◽  
Diet Overlap ◽  
Data Matrix ◽  
Pseudopleuronectes Americanus ◽  
Predator Species ◽  
Benthic Composition

Feeding relationships of various fish species, and their relationship to the composition of the surrounding sediments, were observed for 1 yr at two sites in the lower Bay of Fundy region. The fishes were the ocean pout (Macrozoarces americanus, Zoarcidae), winter flounder (Pseudopleuronectes americanus, Pleuronectidae), plaice (Hippoglossoides platessoides, Pleuronectidae), cod (Gadus morhua, Gadidae), and witch flounder (Glyptocephalus cynoglossus, Pleuronectidae). After reducing the size of the data matrix by removing redundant variables, we used discriminant function analysis to assess interspecific diet overlap and the degree to which stomach contents reflect benthic composition. Variables were ranked by their power to discriminate in pairwise comparisons among fish species and between a given fish species and benthic grab samples. Many amphipods are utilized to an equal or greater extent than their abundances in the sediments would suggest. Many annelids are underutilized. Predation by each fish species was a selective process, and interspecific diet differences are related to the morphology of the predator and the behavior and microhabitat of the prey. The fishes diets, however, are also correlated with spatial and temporal changes in the benthic composition. Specific examples are presented. As benthic food abundance increased in the surrounding sediments all predator species increased their food consumption and interspecific diet overlap declined. In some cases the degree of exploitation depended upon the size rather than the abundance of the prey item.

Marine Fish Tissue Culture

1963 ◽  
Vol 20 (3) ◽  
pp. 679-684 ◽  
Author(s):  
P. M. Townsley ◽  
H. G. Wight ◽  
M. A. Scott
Keyword(s):  
Tissue Culture ◽  
Marine Fish ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
White Perch ◽  
Kidney Tissue ◽  
Fish Tissue ◽  
Pseudopleuronectes Americanus ◽  
Myoxocephalus Scorpius ◽  
Raja Radiata

Cell proliferation of tissue explants of different organs from marine fish has been achieved in a nutrient solution composed of Medium 199 plus 10% human serum. Fin, spleen, heart, kidney, liver, gonad, brain, uterus, and thymus tissues have been cultured. The tissues were obtained from sexually mature Atlantic cod (Gadus morhua), white perch (Roccus americanus) winter flounder (Pseudopleuronectes americanus), thorny skate (Raja radiata), American goosefish (Lophius americanus), pollock (Pollachius virens), and shorthorn sculpin (Myoxocephalus scorpius). An actively dividing cell culture of flounder kidney cells prepared by mechanical disruption of the kidney tissue was maintained through serial transfers over several months. Heart explants from the cod vigorously pulsated in tissue culture.

Infectivity of Trypanosoma murmanensis to leeches (Johanssonia sp.)

1977 ◽  
Vol 55 (10) ◽  
pp. 1698-1700 ◽  
Author(s):  
R. A. Khan
Keyword(s):  
Marine Fish ◽  
Gadus Morhua ◽  
Developmental Stages ◽  
Infected Fish ◽  
Winter Flounder ◽  
Pseudopleuronectes Americanus

Experiments were designed to test the infectivity of trypomastigotes of Trypanosoma murmanensis to leeches at intervals after metatrypomastigotes had initiated infections in marine fish. Infectivity was determined by the presence of developmental stages in recently emerged leeches (Johanssonia sp.) that had fed on experimentally infected fish. A total of 1235 leeches were used in this study. The results indicate that the three morphotypes can initiate infections in leeches. Moreover, some trypanosomes are infective at least 24 h after transmission (16 (67%) leeches became infected). Few leeches acquired infections after feeding on infected winter flounder (Pseudopleuronectes americanus) between 2 and 12 days and on a cod (Gadus morhua) 4–5 days, but all those which fed 7 through 93 day s on five species of marine teleosts became infected. Some of the leeches transmitted infections to uninfected cod. It is believed that the leeches which harboured no developmental stages might not have ingested trypanosomes.

scholarly journals Regional typology of spring vegetation in Parc Ela (Grisons, Switzerland)

2021 ◽  
Vol 2 ◽  
pp. 257-274
Author(s):  
Hallie Seiler ◽  
Daniel Küry ◽  
Regula Billeter ◽  
Jürgen Dengler
Keyword(s):  
Species Richness ◽  
Environmental Variables ◽  
Vascular Plant ◽  
Detrended Correspondence Analysis ◽  
Conservation Strategy ◽  
Soil Reaction ◽  
Ecological Indicator ◽  
Ecological Value ◽  
Water Conductivity ◽  
Regional Survey

Aims: The spring habitats of Central Europe are insular biotopes of high ecological value. Although subject to severe exploitation pressures, they do not yet have a comprehensive protection status in Switzerland. Contributing to this challenge is the controversy involved with their syntaxonomic classification. In the context of the development of a regional conservation strategy and the establishment of a national inventory of Swiss springs, we carried out a regional survey of spring vegetation and aimed to translate this into a classification system. Study area: Montane and subalpine zones of Parc Ela (Grisons, Switzerland). Methods: We selected 20 springs to cover different regions, elevations and bedrock types within the park. In each of them we recorded complete vascular plant and bryophyte composition as well as a range of environmental variables in three 1-m² plots that were placed to reflect the heterogeneity within the spring. After running an unsupervised classification with modified TWINSPAN, the distinguished vegetation units were characterized in terms of diagnostic species, species richness and environmental variables and placed within the syntaxonomic system. Results: Species richness was high (total species 264, mean 21.7 species in 1 m2). The two most important environmental gradients of the ordination were elevation/water conductivity and insolation/water pH/soil reaction EIV. We distinguished seven communities within two main groups. Conclusions: All unshaded springs, including those over siliceous bedrock, could be assigned to a broadly defined Cratoneurion. The petrifying springs were not strongly distinguishable floristically from other base-rich springs. The forest springs, although often not clearly differentiated from their unshaded counterparts, could be provisionally divided into the alliances Caricion remotae and Lycopodo europaei-Cratoneurion commutati. As there is a certain threat to these habitats in the park due to anthropogenic influence, protection measures are recommended, most importantly the appropriate management of alpine pastures. Taxonomic reference: Juillerat et al. (2017) for vascular plants, Meier et al. (2013) for bryophytes. Abbreviations: ANOVA = analysis of variance; DCA = detrended correspondence analysis; EIV = ecological indicator value; FOEN = Federal Office of the Environment (Switzerland); NCHO = Ordinance on the Protection of Nature and Cultural Heritage; SD = standard deviation; TWINSPAN = Two Way Indicator Species Analysis; WPA = Federal Act on the Protection of Waters.

scholarly journals Scottish lobster fisheries and environmental variability

2015 ◽  
Vol 72 (suppl_1) ◽  
pp. i211-i224 ◽  
Author(s):  
H. A. Lizárraga-Cubedo ◽  
I. Tuck ◽  
N. Bailey ◽  
G. J. Pierce ◽  
A. F. Zuur ◽  
...  
Keyword(s):  
Total Variation ◽  
Environmental Variables ◽  
Cross Correlation ◽  
Environmental Variability ◽  
Spatial Scales ◽  
Multivariate Techniques ◽  
Sea Level Pressure ◽  
Fishery Data ◽  
Components Analysis ◽  
Catch Rates

Abstract Variability in the fluctuations of two Scottish lobster populations, the Hebrides and Southeast, was investigated from available long dataseries of fishery and environmental variables. In a multivariate context, relationships between selected environmental variables and the fishery data were studied at different spatial and temporal (annual, spring, and autumn) scales and from individual and overall sampled fleet. Multivariate techniques such as cross-correlation function, principal components analysis, and redundancy analysis confirmed that the capture of lobsters was strongly influenced by sea surface temperature, windspeed, and sea level pressure throughout the year, and this dependence affected the duration of the fishery. There were evident differences in the patterns of environmental variables for both regions. In the Hebrides, the total variation (42%) of the interaction fishery-environmental variables for spring and autumn fisheries could be attributed to the environmental variables in an 89%. For the Southeast, spring fishery was more affected by changes in the environment, with a total variation of 34%, from which 85% could be explained by the environmental variables tested, than autumn fishery where catches and catch rates may be more affected by the way individual vessel and sampled fleet operate. Two elements were identified, Hebrides and Southeast spring and autumn fisheries. The Hebrides lobster population is strongly influenced by density-independence processes at all spatial scales. The Southeast fishery is also driven by environmental processes, with higher correlations for recruits with differences at small and large spatial scales.

Sign in / Sign up

Export Citation Format

Share Document