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.

Evaluation of spatiotemporal imputations for fishing catch rate standardization

2017 ◽  
Vol 74 (9) ◽  
pp. 1348-1361
Author(s):  
Ross J. Marriott ◽  
Berwin A. Turlach ◽  
Kevin Murray ◽  
David V. Fairclough
Keyword(s):  
High Growth ◽  
Catch Rate ◽  
Commercial Fishing ◽  
Data Sets ◽  
Rate Data ◽  
Fishing Activity ◽  
Fish Stocks ◽  
Base Method ◽  
Catch Rates ◽  
Over Time

As commercial fishing activity shifts to target different grounds over time, spatial gaps can be created in catch rate data, leading to biases in derived indices of fish abundance. Imputation has been shown to reduce such biases. In this study, the relative performance of several imputation methods was assessed using simulated catch rate data sets. Simulations were carried out for three fish stocks targeted by a commercial hook-and-line fishery off the southwestern coast of Australia: snapper (Chrysophrys auratus), West Australian dhufish (Glaucosoma hebraicum), and baldchin groper (Choerodon rubescens). For high-growth scenarios, the mean squared errors (MSEs) of geometric and linear imputations were lower, indicating higher accuracy and precision than that for base method (constant value) imputations. For low-growth scenarios, the lowest MSEs were achieved for base method imputations. However, for the final standardized and imputed abundance indices, the base method index consistently demonstrated the largest biases. Our results demonstrate the importance of selecting an appropriate imputation method when standardizing catch rates from a commercial fishery that has changed its spatial pattern of fishing over time.

scholarly journals Using catch rate data for simple cost-effective quota setting in the Australian spanner crab (Ranina ranina) fishery

2010 ◽  
Vol 67 (8) ◽  
pp. 1538-1552 ◽  
Author(s):  
Michael F. O'Neill ◽  
Alexander B. Campbell ◽  
Ian W. Brown ◽  
Ron Johnstone
Keyword(s):  
Decision Rules ◽  
Cost Effective ◽  
Catch Rate ◽  
Management Decision ◽  
Rate Data ◽  
Total Allowable Catch ◽  
Management Procedure ◽  
Annual Total ◽  
New Methodologies ◽  
Catch Rates

Abstract O'Neill, M. F., Campbell, A. B., Brown, I. W., and Johnstone, R. 2010. Using catch rate data for simple cost-effective quota setting in the Australian spanner crab (Ranina ranina) fishery. – ICES Journal of Marine Science, 67: 1538–1552. For many fisheries, there is a need to develop appropriate indicators, methodologies, and rules for sustainably harvesting marine resources. Complexities of scientific and financial factors often prevent addressing these, but new methodologies offer significant improvements on current and historical approaches. The Australian spanner crab fishery is used to demonstrate this. Between 1999 and 2006, an empirical management procedure using linear regression of fishery catch rates was used to set the annual total allowable catch (quota). A 6-year increasing trend in catch rates revealed shortcomings in the methodology, with a 68% increase in quota calculated for the 2007 fishing year. This large quota increase was prevented by management decision rules. A revised empirical management procedure was developed subsequently, and it achieved a better balance between responsiveness and stability. Simulations identified precautionary harvest and catch rate baselines to set quotas that ensured sustainable crab biomass and favourable performance for management and industry. The management procedure was simple to follow, cost-effective, robust to strong trends and changes in catch rates, and adaptable for use in many fisheries. Application of such “tried-and-tested” empirical systems will allow improved management of both data-limited and data-rich fisheries.

Using logbook‐based catch‐rate data to detect yellow eel population trends in the southern Baltic Sea

2021 ◽  
Author(s):  
Malte Dorow ◽  
Wolf‐Christian Lewin ◽  
Dietmar Lill ◽  
Claus Ubl ◽  
Jens Frankowski
Keyword(s):  
Baltic Sea ◽  
Catch Rate ◽  
Population Trends ◽  
Rate Data ◽  
Southern Baltic Sea ◽  
Yellow Eel ◽  
Southern Baltic

Integrating imputation and standardization of catch rate data in the calculation of relative abundance indices

2011 ◽  
Vol 109 (1) ◽  
pp. 157-167 ◽  
Author(s):  
Thomas R. Carruthers ◽  
Robert N.M. Ahrens ◽  
Murdoch K. McAllister ◽  
Carl J. Walters
Keyword(s):  
Relative Abundance ◽  
Catch Rate ◽  
Rate Data ◽  
Abundance Indices

scholarly journals Did over-reliance on commercial catch rate data precipitate the collapse of northern cod?

2005 ◽  
Vol 62 (6) ◽  
pp. 1139-1149 ◽  
Author(s):  
Peter A. Shelton
Keyword(s):  
Population Size ◽  
Functional Relationship ◽  
Catch Rate ◽  
Research Vessel ◽  
Rate Data ◽  
Commercial Catch ◽  
Stock Size ◽  
Functional Relationships ◽  
Northern Cod ◽  
Catch Rates

Abstract It has been suggested that a number of “lessons” can be learned from the collapse of the northern cod stock off Newfoundland and Labrador. However, not all purported lessons have been validated with available data. One lesson is thought to be that over-reliance on commercial catch rate data and an incorrect assumption regarding the functional relationship between catch rate and population size were major contributors to overestimating stock size, precipitating the collapse. The current study describes calibration approaches used in assessments, and evaluates alternative functional relationships between commercial catch rates and stock size. In addition, historical population size is re-estimated using only research vessel data and compared with estimates obtained based on both commercial catch rate and research vessel data. Calibration with commercial catch rate contributed to overestimating stock size in some years, but there is no evidence that the assumed functional relationship between commercial catch rate and population size was a significant factor in the collapse.

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.

scholarly journals Reporting time period matters: quantifying catch rates and exploring recall bias from fisher interviews in Thailand

2018 ◽  
Vol 75 (12) ◽  
pp. 2114-2122 ◽  
Author(s):  
Lindsay Aylesworth ◽  
Ting-Chun Kuo
Keyword(s):  
Fisheries Management ◽  
Data Sets ◽  
Multiple Time ◽  
Recall Bias ◽  
External Data ◽  
Time Period ◽  
The Status ◽  
The Mean ◽  
Catch Rates ◽  
Reported Data

Catch rates reported by fishers are commonly used to understand the status of a fishery, but the reliability of fisher-reported data is affected by how they recall such information. Recalling catch may be influenced by the choice of reporting time period. Using interview data from fishers in Thailand, we investigated (1) how the time period for which fishers report their catch rates (e.g., per day or month) correlates with annual catch estimates and (2) the potential of recall bias when fishers reported multiple catch rates. We found that the annual catch estimates of fishers who reported on a shorter time period (haul, day) were significantly higher than those reported on a longer time period (month, year). This trend held true when individual fishers reported over multiple time periods, suggesting recall bias. By comparing fisher reports with external data sets, we identified that the mean across all reports was most similar to other data sources, rather than any time period. Our research has strong implications in using fishers’ knowledge for fisheries management.

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.

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.

scholarly journals Optimal Spacing of Pheromone Traps for Monitoring the Tobacco Moth, Ephestiaelutella (Hübner) (Lepidoptera: Phyralidae), in Tobacco Warehouses

2011 ◽  
Vol 24 (6) ◽  
pp. 289-292
Author(s):  
T Imai ◽  
Y Kasaishi
Keyword(s):  
Insect Pests ◽  
Catch Rate ◽  
Trap Density ◽  
Pheromone Traps ◽  
Release Point ◽  
Capture Ratio ◽  
Optimal Spacing ◽  
Catch Rates ◽  
Scientific Rationale

AbstractPheromone traps have been widely used for monitoring insect pests in tobacco factories and warehouses. Generally, these traps are placed 10-20 m apart, although a precise scientific rationale for this practice is not available. We examined the effect of trap density on the recovery and localization of tobacco moths released in a 42.3 × 36.5 × 4.0 m tobacco warehouse compartment (1540 m2). In single-trap experiments (0.06 traps/100m2), 15-51% (33% on average) of the released male moths were captured. The capture ratio was not correlated with the distance between the trap and the release point; the highest catch rate was attained when a trap was placed at the most distant position: 47 m from the release point. Capture data from experiments using groups of 4-23 traps revealed that the highest catch rates were always attained by the trap nearest the release point when more than eight traps (0.5 traps/100 m2) were set. These results indicate that the number of traps required for monitoring purposes should be changed - one trap is sufficient for detecting the presence or absence of infestation in a 1540 m2 warehouse compartment (0.06 traps/100 m2); more than eight traps (0.5 traps/100 m2) should be set for localization, allowing the location of the infestation to be inferred from the trap with the highest catch rate.

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