scholarly journals Using catch-per-unit-effort data to solve spatial problems in Orange Roughy abundance estimates

2021 ◽  
Author(s):  
◽  
Max Schofield
Keyword(s):  
Catch Rate ◽  
Additional Parameter ◽  
Catch Per Unit Effort ◽  
Unknown Parameters ◽  
Orange Roughy ◽  
The Andes ◽  
Production Models ◽  
New Information ◽  
Catch Rates ◽  
Habitat Damage

<p>This thesis describes a thorough analysis of the Andes Complex orange roughy fishery, which started in 1991 and continues to date. The Andes Complex orange roughy fishery displays a rapid initial decline in catch rate, followed by a prolonged period of relatively stable catch rate. This trend is the classic feature of a hyperdepletion catch rate. The trends in the observed Andes Complex orange roughy catch rates were explored through the development of eight modified Schaefer Surplus Production Models (SPM). Each model applied a hypothesis about a mechanism catalysing the observed trend of the fishery. The SPM was modified by either adding new information to the model, or an additional parameter. The fits of the modified models were optimised to elucidate values of unknown parameters in the SPM, and these were used to create estimated abundance indicies for each model. Then I compared each index to the observed abundance index (catch rate), derived following an Exploratory Analysis. The best candidate models, which had the smallest likelihoods, BIC values, and best visual fits, were those assuming population growth rate changed midway through the fishery, or that the population size decreased following habitat damage (from trawling).</p>

scholarly journals Using catch-per-unit-effort data to solve spatial problems in Orange Roughy abundance estimates

2021 ◽  
Author(s):  
◽  
Max Schofield
Keyword(s):  
Catch Rate ◽  
Additional Parameter ◽  
Catch Per Unit Effort ◽  
Unknown Parameters ◽  
Orange Roughy ◽  
The Andes ◽  
Production Models ◽  
New Information ◽  
Catch Rates ◽  
Habitat Damage

<p>This thesis describes a thorough analysis of the Andes Complex orange roughy fishery, which started in 1991 and continues to date. The Andes Complex orange roughy fishery displays a rapid initial decline in catch rate, followed by a prolonged period of relatively stable catch rate. This trend is the classic feature of a hyperdepletion catch rate. The trends in the observed Andes Complex orange roughy catch rates were explored through the development of eight modified Schaefer Surplus Production Models (SPM). Each model applied a hypothesis about a mechanism catalysing the observed trend of the fishery. The SPM was modified by either adding new information to the model, or an additional parameter. The fits of the modified models were optimised to elucidate values of unknown parameters in the SPM, and these were used to create estimated abundance indicies for each model. Then I compared each index to the observed abundance index (catch rate), derived following an Exploratory Analysis. The best candidate models, which had the smallest likelihoods, BIC values, and best visual fits, were those assuming population growth rate changed midway through the fishery, or that the population size decreased following habitat damage (from trawling).</p>

Fish and invertebrate by-catch in the crab pot fishery in the Isle of Man, Irish Sea

2017 ◽  
Vol 98 (8) ◽  
pp. 2099-2111
Author(s):  
Fikret Öndes ◽  
Michel J. Kaiser ◽  
Lee G. Murray
Keyword(s):  
Irish Sea ◽  
Target Species ◽  
Catch Per Unit Effort ◽  
Isle Of Man ◽  
Ecosystem Effects ◽  
By Catch ◽  
Catch Rates ◽  
Taxonomic Groups ◽  
Catch Composition ◽  
Autumn And Winter

Baited trap or pot fisheries are considered to have relatively few wider ecosystem effects on the marine environment, particularly when compared with towed mobile fishing gear. However, this assumption is rarely tested in the field. This study aimed to determine the composition of non-target species that occur in crustacean pots and to assess spatial and temporal differences in catches in the waters around the Isle of Man, Irish Sea. The data were collected using fishery independent surveys and a questionnaire study. Based on fishery independent surveys, a total of five taxonomic groups and 43 species occurred as by-catch. The dominant by-catch species was velvet crab Necora puber. The by-catch per unit effort (BPUE) for all of the non-target species was low particularly in comparison to towed bottom gear fisheries around the Isle of Man. BPUE of species composition varied considerably between different locations around the Isle of Man. The results of both the fishery independent and questionnaire data suggested that the by-catch rates varied with season with peak BPUE occurring in spring which then declined into autumn and winter. By-catch composition did not decrease significantly with an increasing target species catch. Overall, by-catch was low relative to target species catch which may be partially attributable to the use of escape panels in pot fisheries in the Isle of Man.

Aspects of the fishery, maturation and net selectivity of the wedge sole (Dicologoglossa cuneata) off south-western Iberia: implications for fishery management

2009 ◽  
Vol 90 (7) ◽  
pp. 1465-1474 ◽  
Author(s):  
Miguel Neves Santos ◽  
Pedro Gil Lino
Keyword(s):  
Fishery Management ◽  
River Mouth ◽  
Mesh Size ◽  
Scientific Basis ◽  
Catch Per Unit Effort ◽  
Important Species ◽  
Gill Net ◽  
Catch Rates ◽  
Log Normal ◽  
First Maturity

The wedge sole (Dicologoglossa cuneata, Moreau 1881) is a commercially important species for the artisanal fleet operating off the south-western Iberian Peninsula. During 2004 and 2005 a study was undertaken aiming to provide a scientific basis for management. Data collection included information on aspects of the fishery, spawning season, size at first maturity, tangle and gill-net selectivity. Seven nominal mesh sizes were used (40, 45 and 50 mm tangle nets and 40, 50, 60 and 70 mm gill-nets). Spawning lasts from December to June, with peaks in March and May. Length at first maturity for females was estimated at 18.5 cm. Catch rates decreased sharply with increasing mesh size, with tangle nets providing the highest yields. The log-normal selectivity model provided the best fit for specimens that were wedged. The higher catch-per-unit-effort of the smaller mesh sizes and the modal length of the fitted selectivity curve being below the size-at-maturity for wedge sole, suggests that the 50 mm nominal mesh size tangle net is the most appropriate for ensuring the fishery sustainability. Nevertheless, the minimum legal size should increase to at least 18 cm and a time–area closure should be implemented off the Guadiana River mouth.

scholarly journals Standardizing catch rates: is logbook information by itself enough?

2008 ◽  
Vol 65 (2) ◽  
pp. 255-266 ◽  
Author(s):  
J. Bishop ◽  
W. N. Venables ◽  
C. M. Dichmont ◽  
D. J. Sterling
Keyword(s):  
Relative Abundance ◽  
Prediction Models ◽  
Expert Knowledge ◽  
External Information ◽  
Linear Regression Models ◽  
Catch Per Unit Effort ◽  
Estimation Model ◽  
Catch Rates ◽  
Logbook Data ◽  
Estimation Models

Abstract Bishop, J., Venables, W. N., Dichmont, C. M., and Sterling, D. J. 2008. Standardizing catch rates: is logbook information by itself enough? – ICES Journal of Marine Science, 65: 255–266. The goal of the work was to maximize the accuracy of standardized catch per unit effort as an index of relative abundance. Linear regression models were fitted to daily logbook data from a multispecies penaeid trawl fishery in which within-vessel changes in efficiency are common. Two model-fitting strategies were compared. The predictive strategy focused on maximizing the explained variance, and the estimation strategy on finding realistic coefficients for important components of changing catchability. Realistic values could not always be obtained, because the regression factors were not orthogonal, and data on the presence of technology were sometimes unreliable or systematically incomplete. It was not possible to separate fishing power from abundance by analysing logbook data alone; it was necessary to incorporate external information within the standardization model. Therefore, the resultant estimation models incorporated external information and expert knowledge by offsets. There was no single best estimation model. Instead, a series of models provided an envelope of possible changes in relative fishing power and prawn abundance since 1970. Compared with the prediction models, the estimation models revealed different trends in relative fishing power and relative abundance.

Folly and fantasy in the analysis of spatial catch rate data

2003 ◽  
Vol 60 (12) ◽  
pp. 1433-1436 ◽  
Author(s):  
Carl Walters
Keyword(s):  
Catch Rate ◽  
Population Trends ◽  
Rate Data ◽  
Fishing Activity ◽  
Time Period ◽  
Abundance Indices ◽  
Catch Rates ◽  
Catch Per Effort

Spatial catch per effort data can provide useful indices of population trends provided that they are averaged so as to correct for effects of changes in the distribution of fishing activity. Simple, nonspatial ratio estimates should not be used in such analyses. The averaging for any time period must necessarily make some assumptions about what catch rates would have been in spatial strata that had not yet, or were no longer, being fished. Ignoring the unfished strata (averaging only over the areas that were fished) amounts to assuming that they behaved the same as the fished strata and can lead to severe hyperdepletion in abundance indices for fisheries that developed progressively over large regions.

scholarly journals Lunar periodicity in catch rate and reproductive condition of adult eastern king prawns, Penaeus plebejus, in coastal waters of south-eastern Queensland, Australia

1996 ◽  
Vol 47 (1) ◽  
pp. 67 ◽  
Author(s):  
AJ Courtney ◽  
DJ Die ◽  
JG McGilvray
Keyword(s):  
Coastal Waters ◽  
Full Moon ◽  
Lunar Cycle ◽  
Catch Rate ◽  
Lunar Phase ◽  
Reproductive Condition ◽  
Ovary Weight ◽  
South Eastern ◽  
New Moon ◽  
Catch Rates

This study examined the lunar and die1 variation in catch rates and reproductive condition of adult eastern king prawns, Penaeus plebejus, in relatively deep (160 m) coastal waters off south- eastern Queensland. Females numerically dominated catches over most of the lunar cycle and constituted 76% of the weight of the catch. Analysis of variance (ANOVA) revealed an interaction between lunar phase and sex; catches peaked during Lunar Phase 3 (full moon � 3 days) and were particularly marked for males. This was the only period during the lunar cycle when the sex ratio approached 1 : 1. There was also an interaction between trawl-time and sex; male catch rates were at a minimum early in the evening, whereas female catch rates were at a maximum then and declined throughout the night. Trawler logbook catch rate data from the same area over a similar period indicated an interaction between lunar cycle and lunar phase. ANOVA revealed an effect of the interaction between phase and sex on the incidence of soft prawns; the incidence of soft males increased during Phase 4 (half moon waning to new moon � 3 days). Ovary weight also varied between phases and was higher during Phases 2 (half moon waxing to full moon � 3 days) and 4 (half moon waning to new moon � 3 days). Trends in the ovary weight and the incidence of histologically mature and ripe females suggested there are two periods of increased spawning activity during each lunar cycle. A cyclic regression fitted to the data explained 93% of the variation in the incidence of ripe females between samples. The influence of these cyclic trends in catch rate and reproductive condition should be considered when monitoring the spawning stock in the fishery and when planning sampling strategies in any future reproductive studies.

Black Bass Diversity: Multidisciplinary Science for Conservation

2015 ◽  
Keyword(s):  
Mixed Model ◽  
Micropterus Salmoides ◽  
Underlying Mechanism ◽  
Treated Wastewater ◽  
Fish Length ◽  
Catch Per Unit Effort ◽  
Explanatory Factors ◽  
Black Bass ◽  
Intersex Condition ◽  
Catch Rates

<em>Abstract</em>.—Reports of testicular oocytes (intersex) in fish are increasing worldwide. Intersex is often associated with estrogens in treated wastewater effluents, but few studies have explored other potentially explanatory factors. Our recent survey of intersex Largemouth Bass <em>Micropterus salmoides</em> in 11 impoundments across Georgia, USA found high incidence (>80%) of intersex fish in some impoundments but none in others. To explore factors associated with intersex in the impoundments, which did not receive wastewater, we examined potential predictor variables that varied among the levels of individual fish, impoundment, or landscape in a binomial mixed-model regression approach. Our model indicated effects of fish length, catch per unit effort (an index of fish density), and impoundment, which was the strongest effect. The probability of intersex was highest in smaller fish from impoundments with the highest catch rates. The underlying mechanism(s) for the impoundment effect remain unclear, but we hypothesize that estrogens excreted by high densities of fish and cyanobacteria may influence intersex. Additional studies are needed to understand the long-term population implications of intersex and the role of other biological and environmental factors, particularly at the impoundment level, in development of the intersex condition.

Biology and Management of Dogfish Sharks

2009 ◽  
Keyword(s):  
Juvenile Fish ◽  
Catch Rate ◽  
Spiny Dogfish ◽  
Commercial Fishery ◽  
Sources Of Information ◽  
Strait Of Georgia ◽  
The Status ◽  
Mean Size ◽  
Catch Rates ◽  
Mature Fish

Abstract.—Spiny dogfish <em>Squalus acanthias </em>have been an important component of the Strait of Georgia fisheries from the late 1800s to the late 1940s, when the fishery collapsed owing to overfishing and changes in market demand. The stock population levels have sustained a commercial fishery of approximately 2,000 metric tons since 1978. Recent concerns regarding the status of dogfish stocks worldwide have reprioritized the status assessment of dogfish in British Columbia. Longline research surveys were conducted for dogfish in the Strait of Georgia in 1986, 1989, and 2005. Additional sources of information are catch and effort data collected through logbook records from the commercial longline fishery. Recent improvements in gear configuration resulted in a switch in the mid-1990s from traditional J hooks to circle hooks, which makes direct comparison of catch rates difficult. In November 2004 a calibration experiment using J hooks and circle hooks demonstrated that, overall, spiny dogfish catch per unit effort (CPUE) for circle-hook gear was 1.6–1.7 times higher than that for J-hook gear. After applying this conversion to the commercial longline CPUE data available for 1980–1984 and 2000–2004, no significant trend in catch rate over time was detected. The catch rate observed in the longline research survey actually increased in 2005 compared to 1986 and 1989. In both fisheries and research data, the proportion of smaller spiny dogfish in the size distribution has increased, reducing the overall mean size. The decline in mean size is probably due to an increase in recruitment of juvenile fish. However, caution in management of this stock is warranted given that the current commercial fishery is now landing a large proportion (estimated 80%) of immature fish. Increased fishing pressure on juveniles could have implications for the abundance of mature fish in upcoming decades.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

2011 ◽  
Keyword(s):  
Population Dynamics ◽  
Channel Catfish ◽  
Mississippi River ◽  
Upper Mississippi River ◽  
Catch Per Unit Effort ◽  
Blue Catfish ◽  
Resource Monitoring ◽  
Flathead Catfish ◽  
Unit Effort ◽  
Catch Rates

<em>Abstract</em>.—Using Long Term Resource Monitoring Program data collected from impounded (Pool 26) and unimpounded (Open River) reaches of the upper Mississippi River, we investigated population dynamics of flathead catfish <em>Pylodictis olivaris</em>, channel catfish <em>Ictalurus punctatus</em>, and blue catfish <em>I. furcatus</em> from random sites located in side channel border (SCB) and main channel border (MCB) habitats. Objectives were to (1) compare trends (1993–2007) of three catfishes collected in Pool 26 and Open River reaches of the upper Mississippi River, and (2) provide needed information to managers on population dynamics through time using a binary gear approach of active (i.e., daytime electrofishing) and passive gears (hoopnetting). Active gears resulted in a higher catch per unit effort (CPUE) of all catfishes in each habitat–reach combination as compared to passive gears. Passive gears resulted in negligible catches of blue catfish and flathead catfishes (e.g., mean of <1 fish/net night). Catch per unit effort using active gear resulted in a greater number of channel catfish captured in Pool 26 compared to the Open River, with Open River SCB habitat having the lowest CPUE in most years. Blue catfish in the Open River had a higher CPUE using active gear as compared to Pool 26, with the Open River MCB having the greatest CPUE. Flathead catfish had a higher CPUE in MCB habitat compared to SCB habitat, with the Open River MCB having the highest CPUE in most years. However, declining trends in flathead catfish appears to be occurring in Open River habitats while trends in flathead catfish appear to be slightly increasing in Pool 26. The most common length-classes captured were substock and stock-sized fish regardless of habitat, species, or reach. Trends for channel catfish were easily determined due to high catch rates; however, more monitoring and enhanced sampling is needed to accurately assess flathead catfish and blue catfish trends and to accurately determine demographics for all three species.

Behavioral inferences from regulatory observer data: catch rate variation in the Scotian Shelf silver hake (Merluccius bilinearis) fishery

1999 ◽  
Vol 56 (2) ◽  
pp. 288-296 ◽  
Author(s):  
D M Gillis
Keyword(s):  
Interference Competition ◽  
Temporal Trends ◽  
Catch Rate ◽  
Rate Variation ◽  
Scotian Shelf ◽  
Apparent Contradiction ◽  
Fishing Vessels ◽  
Catch Rates ◽  
Silver Hake ◽  
Merluccius Bilinearis

The detailed spatial and temporal data collected for the regulation of the silver hake (Merluccius bilinearis) fishery on the Scotian Shelf provide a unique opportunity to test hypotheses about variability in catch rates on the scale of individual trawls. I used these data to examine vessel interactions and long-term temporal trends in catchability. An index of course linearity, derived from observed positions, times, and speeds of fishing vessels, indicated that interference competition was present in the fishery. However, catch rate did not decline with local vessel density. This apparent contradiction is consistent with fleet dynamic theory and suggests that the direct examination of catch rates is a poor test for interference in the retrospective analysis of fisheries data. The study of extended periods of high, localized fishing activity revealed a cycle in catch rates with periods of about 6 days. Such periods may represent an interaction between tidal, diel, and (or) technological factors. Although more study is required to identify the cause of these cycles, their existence should be considered in the design of surveys and other population studies using catch and effort data.

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