Recurrent Group Analysis of Species Assemblages of Demersal Fish in the Gulf of Guinea

1968 ◽  
Vol 25 (7) ◽  
pp. 1405-1421 ◽  
Author(s):  
E. W. Fager ◽  
A. R. Longhurst
Keyword(s):  
Survey Data ◽  
Computer Analysis ◽  
Group Analysis ◽  
Demersal Fish ◽  
Species Assemblages ◽  
Trawl Survey ◽  
Wide Sense ◽  
Subjective Analysis ◽  
Major Species ◽  
Species Groups

Recurrent species groups were formed by computer analysis from the data on occurrence of demersal fish at 480 trawl stations in the tropical eastern Atlantic; these recurrent groups were then marshalled into a small number of major species assemblages, or communities in the wide sense, on the basis of intergroup relationships. These assemblages proved to be remarkably similar in composition and ecology to the communities of demersal fish recognized earlier by a number of authors from their subjective analysis of trawling survey data in this region. The computer analysis provided finer detail on both the structure and distribution of the assemblages and their constituent groups. This confirmation of the reality of the subjectively recognized communities suggests (1) that the recognition of such assemblages by subjective methods has a place in the assessment of multispecies fish resources but (2) that where the method is practicable, the machine processing of recurrent species groups in the analysis of trawl survey data can be a valuable tool in resource evaluation.

Odontopleura (Trilobita, Silurian), and a method of constrained congruency analysis

1990 ◽  
Vol 64 (4) ◽  
pp. 600-614 ◽  
Author(s):  
Jonathan M. Adrain ◽  
Brian D. E. Chatterton
Keyword(s):  
Cladistic Analysis ◽  
Canadian Arctic ◽  
Wide Distribution ◽  
Parsimony Analysis ◽  
Directed Tree ◽  
Shelf Slope ◽  
Major Species ◽  
Species Groups ◽  
The Universe ◽  
A New Species

Odontopleura (Odontopleura) arctica, a new species of odontopleurine trilobite, is described from the Canadian Arctic. A method of cladistic analysis is detailed. Parsimony analysis should be performed treating all characters as unordered. The universe of directed trees implied by the resulting rootless network(s) can then be examined and a preferred tree selected by a criterion of congruency. Namely, the most parsimonious directed tree that accommodates the most congruent arrangement of character-states should be taken as the preferred cladogram. Since this is essentially a general congruency method operating within the constraints of parsimony, it is termed “constrained congruency.” The method is applied to the genus Odontopleura, resulting in the recognition of two major species groups, the nominate subgenus and Sinespinaspis n. subgen. Odontopleura (Ivanopleura) dufrenoyi Barrande is tentatively included in the genus, but considered too poorly known for cladistic analysis. Species assigned to Odontopleura (Odontopleura) include Odontopleura ovata Emmrich, Odontopleura brevigena Chatterton and Perry, Odontopleura (Odontopleura) arctica n. sp., and Diacanthaspis serotina Apollonov. Species assigned to Sinespinaspis n. subgen. include Taemasaspis llandoveryana Šnajdr, Odontopleura greenwoodi Chatterton and Perry, Odontopleura maccallai Chatterton and Perry, and Odontopleura nehedensis Chatterton and Perry. Odontopleura bombini Chatterton and Perry is tentatively placed in synonymy with Odontopleura nehedensis. The genus had a wide distribution throughout the Early and Middle Silurian, due to preferences for deep-water, distal shelf or shelf-slope transition zone habitats.

scholarly journals Decadal‐Scale Variation in Mean Trophic Level in Beibu Gulf Based on Bottom‐Trawl Survey Data

2021 ◽  
Vol 13 (3) ◽  
pp. 174-182
Author(s):  
Li Su ◽  
Zuozhi Chen ◽  
Kui Zhang ◽  
Youwei Xu ◽  
Shannan Xu ◽  
...  
Keyword(s):  
Survey Data ◽  
Trophic Level ◽  
Bottom Trawl ◽  
Beibu Gulf ◽  
Trawl Survey ◽  
Bottom Trawl Survey ◽  
Decadal Scale ◽  
Mean Trophic Level ◽  
Scale Variation

Demersal fish biomass size spectra on the Scotian Shelf, Canada: species replacement at the shelfwide scale

1997 ◽  
Vol 54 (8) ◽  
pp. 1725-1735 ◽  
Author(s):  
D E Duplisea ◽  
S R Kerr ◽  
L M Dickie
Keyword(s):  
Time Series ◽  
Body Weight ◽  
Energy Input ◽  
Demersal Fish ◽  
Species Group ◽  
Total Biomass ◽  
Species Replacement ◽  
Scotian Shelf ◽  
Size Spectra ◽  
Species Groups

Three parameters were derived from annual biomass size spectra constructed for a 22-year time series of demersal fish data for the entire Scotian Shelf: (i) total sampled biomass density, (ii) modal body weight, and (iii) the shape of the various biomass size spectra. Temporal variability of these parameters was compared among six species groups and between the species groups and their total. Species-group biomass varied more over the time series than did the total biomass, indicating the presence of a system factor. Conversely, modal body weight was as variable, and sometimes more variable, for the total than it was within species groups, indicating variability mainly at the species level. The shape of the biomass size spectrum showed annual differences in variability owing mainly to contributions of species groups. This variability was higher than variability in the combined species totals. We conclude that total biomass is limited at the combined species (systemwide) level because it depends on energy input to the system. Variability is greater at the species group (subsystem) level because the multiage species-group biomasses do not equally reflect a given energy limitation. Neither modal body weight nor the shape of the biomass spectrum is sensitive to the degree of taxonomic aggregation, suggesting that both measures are independent of energy input (primary production). We found no evidence of consistent species replacement trends on the shelfwide scale and conclude that diffuse replacement best describes species succession on the Scotian Shelf as a whole.

scholarly journals Demersal fish assemblages and habitat characteristics on the continental shelf and upper slope of the north-western Mediterranean

2000 ◽  
Vol 80 (6) ◽  
pp. 981-988 ◽  
Author(s):  
Montserrat Demestre ◽  
Pilar Sánchez ◽  
Pere Abelló
Keyword(s):  
Continental Shelf ◽  
Fish Species ◽  
Fish Assemblages ◽  
Demersal Fish ◽  
Western Mediterranean ◽  
Habitat Characteristics ◽  
Species Assemblages ◽  
The North ◽  
Benthic Sediments ◽  
Upper Slope

Continental shelf and upper slope fish communities were studied along the Catalan coast based on 66 experimental bottom otter trawls. A total of 79 demersal fish species were studied by means of cluster analysis and multi-dimensional scaling (MDS) ordination for community structure. Analysis revealed the existence of five major location clusters. Similarity percentage analysis (SIMPER) was determined by comparing the dissimilarity between two groups of samples using the discriminating species. Geomorphological characteristics, bottom substratum and depth showed direct influences on species assemblages. High correlation between the biotic data samples and depth was observed. The fish species assemblages identified five main demersal fish associations which corresponded with the five location clusters and with five benthic sediments (mud of the upper slope, sand and gravel, mud of the shelf, muddy-sand and sand with rocky outcrops).

scholarly journals Selecting MPAs to conserve groundfish biodiversity: the consequences of failing to account for catchability in survey trawls

2008 ◽  
Vol 66 (1) ◽  
pp. 82-89 ◽  
Author(s):  
Helen M. Fraser ◽  
S. P. R. Greenstreet ◽  
Gerjan J. Piet
Keyword(s):  
Species Diversity ◽  
Survey Data ◽  
North Sea ◽  
Marine Protected Areas ◽  
Fishing Effort ◽  
Trawl Survey ◽  
Fishing Activity ◽  
Diversity Issues ◽  
Species Specific ◽  
Fish Species Diversity

Abstract Fraser, H. M., Greenstreet, S. P. R., and Piet, G. J. 2009. Selecting MPAs to conserve groundfish biodiversity: the consequences of failing to account for catchability in survey trawls. – ICES Journal of Marine Science, 66: 82–89. Fishing has affected North Sea groundfish species diversity. Defining Marine Protected Areas (MPAs) to address this will rely on groundfish surveys. Species-specific catch efficiencies vary between trawl gears, and apparent species diversity distributions are influenced by the type of gear used in each survey. It may be that no single survey depicts actual diversity distributions. Two MPA scenarios designed to protect groundfish species diversity are described, the first based on unadjusted International Bottom Trawl Survey data and the second based on the same data adjusted to take account of catchability. Spatial overlap between these scenarios is low. Assuming that the adjusted data best describe the actual species diversity distribution, the level of diversity safeguarded by MPAs, based on unadjusted data, is determined. A fishing effort redistribution model is used to estimate the increase in fishing activity that is likely to occur in MPAs that take catchability into account, if closed areas based solely on the unadjusted groundfish data were implemented. Our results highlight the need to take survey-gear catchability into account when designating MPAs to address fish-species diversity issues.

Abundance of demersal fish resources in the Persian Gulf and Oman Sea

2006 ◽  
Vol 86 (6) ◽  
pp. 1455-1462 ◽  
Author(s):  
T. Valinassab ◽  
R. Daryanabard ◽  
R. Dehghani ◽  
G.J. Pierce
Keyword(s):  
Persian Gulf ◽  
Central Area ◽  
Demersal Fish ◽  
Total Biomass ◽  
Trawl Survey ◽  
Important Species ◽  
Fish Resources ◽  
Oman Sea ◽  
Commercially Important ◽  
The Persian Gulf

We report on results of a trawl survey during 2003–2004 to assess the abundance of demersal fish resources in the Persian Gulf and Oman Sea. Samples were taken at a total of 316 trawl stations selected following a stratified random procedure. Catch rates (catch per unit area, CPUA) and total biomass were estimated. Total demersal fish biomass was estimated to be approximately 73,000 tonnes in Persian Gulf waters and approximately 39,000 tonnes in the Oman Sea. The lowest CPUA was recorded in the west of the study area (stratum A, approximately 1700 kg/n.m.2) and the highest in the east (stratum Q, 13943.4 kg/n.m.2), although density of commercially important species was higher in the central area (stratum K). Catch rate and biomass varied significantly in relation to seabed depth. Commercially important demersal species made up around 60% of the estimated total biomass. The most abundant species groups were rays, catfish, grunts, nemipterids and carangids. Several important species (e.g. silver pomfret, croakers and sharks) appear to have declined since the late 1970s while others, such as rays and catfish, have increased.

Validation of deep-sea coral and sponge distribution models in the Aleutian Islands, Alaska

2017 ◽  
Vol 75 (1) ◽  
pp. 199-209 ◽  
Author(s):  
Christopher N Rooper ◽  
Rachel Wilborn ◽  
Pamela Goddard ◽  
Kresimir Williams ◽  
Richard Towler ◽  
...  
Keyword(s):  
Survey Data ◽  
Deep Sea ◽  
Goodness Of Fit ◽  
Bottom Trawl ◽  
Aleutian Islands ◽  
Trawl Survey ◽  
Bottom Trawl Survey ◽  
Spatial Management ◽  
Model Predictions ◽  
Deep Sea Corals

Abstract Spatial management of vulnerable benthic ecosystem components such as deep-sea corals and sponges requires adequate maps of their distribution. These maps are often based on statistical models of survey data. The objective of this project was to validate the predictions of existing presence or absence and abundance models of deep-sea corals and sponges in the Aleutian Islands that were based on bottom trawl survey data. Model validation was conducted by comparing bottom trawl survey model predictions to the observations of an in situ camera survey conducted at randomly selected locations. The measures of goodness of fit (area-under-the-receiver-operator-curve, AUC) for the bottom trawl survey model predictions of camera survey observations ranged from 0.59 to 0.77 (for sponges and coral, respectively) and indicated that the bottom trawl survey models predicted the probability of presence for corals accurately across the Aleutian Islands. The bottom trawl survey models explained as little as 3% of the variability in Stylasteridae density and up to 17% of the variability in coral density. These results indicate that models of deep-sea coral distributions based on presence and absence data from bottom trawl surveys can be accurate and can provide useful information for spatial management of these vulnerable taxa. However, for some other taxa, such as sponges, care should be taken interpreting the results of bottom trawl survey models. An interesting finding of this study was that the residuals from the bottom trawl survey model-camera density relationships were negative in areas that remained open to fishing after 2005, possibly indicating an effect of continued bottom trawling on the abundance of corals in these areas. This study highlights the importance of validating models of species distribution using independent surveys, so that the results can be used with confidence to support decision-making processes.

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