Diffusion of American lobster (Homarus americanus) in Northumberland Strait, Canada

2009 ◽  
Vol 66 (4) ◽  
pp. 659-671 ◽  
Author(s):  
Cornelia Elizabeth den Heyer ◽  
E. Michael P. Chadwick ◽  
Jeffrey A. Hutchings
Keyword(s):  
Power Analysis ◽  
Sexual Maturity ◽  
Mean Square Displacement ◽  
Homarus Americanus ◽  
Small Sample ◽  
American Lobster ◽  
Fishing Gear ◽  
Positive Linear Correlation ◽  
Small Sample Sizes ◽  
Trawl Surveys

We tested the hypothesis that American lobster ( Homarus americanus ) movement can be described as diffusion. In 2001 and 2002, 3689 lobsters, captured by experimental trap and trawl surveys, were tagged and released in Northumberland Strait, Canada. Recaptures (n = 413) were reported by roughly 200 commercial fishermen, up to 3 years after release. Only six lobsters, all females, were recaptured more than once. Recapture rates were marginally higher for males (male 12%, female 10%) and varied with area of release (range: 5%–12%) and the fishing gear used for tagging (trap 12%, trawl 11%). Maximum and mean displacements between release and recapture were 58.3 and 12.3 km, respectively. The positive linear correlation between mean square displacement (MSD) and time between release and recapture provides evidence for diffusion. We calculate a diffusion coefficient (D) of 13 km2·week–1; there was no difference in D between sexes. A power analysis showed that MSD is underestimated at small sample sizes. There were insufficient data to test for differences in D associated with sexual maturity or shell hardness at time of release. During the summer in Northumberland Strait, the lobster population spreads about 20 km. The demographic consequences of seasonal diffusion of lobster warrant study.

Bootstrap confidence limits for groundfish trawl survey estimates of mean abundance

1997 ◽  
Vol 54 (3) ◽  
pp. 616-630 ◽  
Author(s):  
S J Smith
Keyword(s):  
Confidence Intervals ◽  
Probability Model ◽  
Small Sample ◽  
Trawl Survey ◽  
Confidence Limits ◽  
Complex Sampling ◽  
Survey Estimates ◽  
Small Sample Sizes ◽  
Complex Sampling Designs ◽  
Trawl Surveys

Trawl surveys using stratified random designs are widely used on the east coast of North America to monitor groundfish populations. Statistical quantities estimated from these surveys are derived via a randomization basis and do not require that a probability model be postulated for the data. However, the large sample properties of these estimates may not be appropriate for the small sample sizes and skewed data characteristic of bottom trawl surveys. In this paper, three bootstrap resampling strategies that incorporate complex sampling designs are used to explore the properties of estimates for small sample situations. A new form for the bias-corrected and accelerated confidence intervals is introduced for stratified random surveys. Simulation results indicate that the bias-corrected and accelerated confidence limits may overcorrect for the trawl survey data and that percentile limits were closer to the expected values. Nonparametric density estimates were used to investigate the effects of unusually large catches of fish on the bootstrap estimates and confidence intervals. Bootstrap variance estimates decreased as increasingly smoother distributions were assumed for the observations in the stratum with the large catch. Lower confidence limits generally increased with increasing smoothness but the upper bound depended upon assumptions about the shape of the distribution.

scholarly journals LARGE EPIBENTHIC INVERTEBRATES IN THE BRAS D’OR LAKES

2002 ◽  
Vol 42 (1) ◽  
Author(s):  
M. John Tremblay
Keyword(s):  
Egg Production ◽  
Carcinus Maenas ◽  
Homarus Americanus ◽  
Strongylocentrotus Droebachiensis ◽  
Green Crab ◽  
American Lobster ◽  
Placopecten Magellanicus ◽  
Cancer Irroratus ◽  
Trawl Surveys ◽  
Epibenthic Invertebrates

The distribution of large epibenthic invertebrates (lobster and crabs, bivalve molluscs and echinoderms) in the Bras d’Or Lakes is reviewed, and possible limiting factors are identified. The review is based on published and unpublished studies, including recent trawl surveys directed at fish, and trapping studies directed at American lobster Homarus americanus and green crab Carcinus maenas. The reduced salinities within the Lakes probably limit the distribution of several species (rock crab Cancer irroratus, sea scallop Placopecten magellanicus and possibly American lobster), particularly during the more sensitive larval period. Lobsters and eastern oysters Crassostrea virginica serve to illustrate the multiple factors limiting epibenthic invertebrate distribution within the Bras d’Or Lakes. Lobsters are less abundant within the Bras d’Or Lakes than on the outer coast of Cape Breton Island. Possible reasons are the reduced salinity and limited cobble bottom substrate in the Bras d’Or Lakes, coupled with low food availability and low egg production. Low egg production may be the result of overfishing of lobsters in the past. The life history and physiology of the eastern oyster appears to be well suited to the areas of the Lakes with warm summer temperatures. The oyster populations in the Bras d’Or Lakes are limited by natural predators (e.g. starfish and green crab), competitors (e.g. blue mussel Mytilus edulis and M. trossulus), and overfishing. The green crab, a new arrival to the Bras d’Or Lakes, will likely have negative effects on bivalves such as oysters, but the overall effect of green crab on the Bras d’Or Lakes food web is difficult to predict. Recent trawl surveys indicate both sea urchins Strongylocentrotus droebachiensis and starfish are present in considerable abundance, but little is known about their ecological roles in the Bras d’Or Lakes.La distribution des grands invertébrés épibenthique (les homards et les crabes, les mollusques bivalves et les échinodermes) dans les lacs du Bras d’Or est examinée et les coefficients possiblement limitatifs sont identifies. La revue est basée sur des études publiées et non-publiées englobant les plus récentesétudes sur la pêche au chalut dirigées vers les poissons et les études sur la pêche aux casiers dirigées vers les homards américains Homarus americanus et les crabes verts Carcinus maenas. Salinités réduites dans les lacs du Bras d’Or limitent probablement la distribution de quelques espèces crabes roches Cancer irroratus, pétoncle géant Placopecten magellanicus et possiblement le homard américain, en particulier, pendent l’époque sensible du larvaire. Les homards et les huîtres de l’Est Crossostrea virginica montrent plusieurs facteurs coefficients limitatifs de la distribution des invertébrés épibenthique dan les lacs du Bras d’Or. Les homards sont moins abondants ici que sur la côte extérieure de L’Ille du Cap Breton. Des explications possibles sont la réduction de l’eau saline du pavé rond limite dans le substratum de lacs, ainsi que la pauvre disponibilité de mangé et la production basse des oeufs. Cette dernière est peut-être le résultat d’un trop grand prise de homards au passè. L’histoire et la physiologie des huîtres semblent être bien adaptés aux lieux des lacs de Bras d’Or, qui ont des temperatures chaudes dan l’été. La population des huîtres dans les lacs est limitée par des proies natures ( ie étoiles de mer et les crabes verts) compétiteurs ( ie. Moules bleus Mytilus edulis et M. trossulus) et une trop grande prise de poissons. Le crabe vert, une arrivée nouvelle dans les lacs du Bras d’Or va sans doute avoir des impacts négatifs sur les bivalues comme les huîtres, mais leurs impacts en general sur la chaîne nutritive est difficile à prédire. Les études les plus recents sur la pêche au chalut montrent qu’il y a ungrand nombre d’oursins de mer Strongylocentrotus droebachiensis et des étoiles de mer, mais on ne connait pas quel est leur rôle écologique dans les lacs du Bras d’Or.

Relative growth, life-history phases, and sexual maturity of American lobster (Homarus americanus)

2010 ◽  
Vol 88 (4) ◽  
pp. 347-358 ◽  
Author(s):  
Kim Émond ◽  
Bernard Sainte-Marie ◽  
Louise Gendron
Keyword(s):  
Life History ◽  
Sexual Maturity ◽  
Body Part ◽  
Homarus Americanus ◽  
American Lobster ◽  
Body Parts ◽  
Growth Phases ◽  
Major Life ◽  
Relative Growth ◽  
Cephalothorax Length

Previous studies of relative growth in crustaceans have focused primarily on body parts representing sexual characters for the purpose of determining size at onset of sexual maturity. We have revisited the relative growth of abdomen and crusher claw in American lobster ( Homarus americanus H. Milne Edwards, 1837) in a general life-history perspective using a broad spectrum of lobster sizes (6–160 mm cephalothorax length (CL)). Growth phases were recognized by inflections in scatterplots of a body-part measurement against CL. The abdomen is characterized by three growth phases in the male and female, whereas the crusher claw has at least three growth phases in the male and at least two in the female. Additionally, we explored relative growth of gonopod and vas deferens for males of 35–150 mm CL. Both organs exhibit a synchronous change from strong to weak positive growth allometry. The growth phases can be associated with major life-history events including the transition from a cryptic to an overt lifestyle and the onset of physiological, functional, and morphometric maturity. The onset of morphometric maturation inferred from relative growth of abdomen and crusher claw precedes functional maturity in females and follows it in males.

scholarly journals Power Analysis for Conjoint Experiments

2020 ◽  
Author(s):  
Julian Schuessler ◽  
Markus Freitag
Keyword(s):  
Power Analysis ◽  
R Package ◽  
Small Sample ◽  
Effect Sizes ◽  
Sample Sizes ◽  
Social Scientists ◽  
Standard Tool ◽  
Sample Size Planning ◽  
Small Sample Sizes ◽  
Power Analyses

Conjoint experiments aiming to estimate average marginal component effects and related quantities have become a standard tool for social scientists. However, existing solutions for power analyses to find appropriate sample sizes for such studies have various shortcomings and accordingly, explicit sample size planning is rare. Based on recent advances in statistical inference for factorial experiments, we derive simple yet generally applicable formulae to calculate power and minimum required sample sizes for testing average marginal component effects (AMCEs), conditional AMCEs, as well as interaction effects in forced-choice conjoint experiments. The only input needed are expected effect sizes. Our approach only assumes random sampling of individuals or randomization of profiles and avoids any parametric assumption. Furthermore, we show that clustering standard errors on individuals is not necessary and does not affect power. Our results caution against designing conjoint experiments with small sample sizes, especially for detecting heterogeneity and interactions. We provide an R package that implements our approach.

Growth of juvenile American lobster Homarus americanus in a changing environment

2016 ◽  
Vol 557 ◽  
pp. 177-187 ◽  
Author(s):  
MD McMahan ◽  
DF Cowan ◽  
Y Chen ◽  
GD Sherwood ◽  
JH Grabowski
Keyword(s):  
Homarus Americanus ◽  
American Lobster ◽  
Changing Environment

Predicting bycatch hotspots based on suitable habitat derived from fishery-independent data

2020 ◽  
Vol 641 ◽  
pp. 159-175
Author(s):  
J Runnebaum ◽  
KR Tanaka ◽  
L Guan ◽  
J Cao ◽  
L O’Brien ◽  
...  
Keyword(s):  
Habitat Suitability ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Gulf Of Maine ◽  
Homarus Americanus ◽  
Management Tool ◽  
American Lobster ◽  
Suitable Habitat ◽  
Climate Conditions ◽  
Suitability Index

Bycatch remains a global problem in managing sustainable fisheries. A critical aspect of management is understanding the timing and spatial extent of bycatch. Fisheries management often relies on observed bycatch data, which are not always available due to a lack of reporting or observer coverage. Alternatively, analyzing the overlap in suitable habitat for the target and non-target species can provide a spatial management tool to understand where bycatch interactions are likely to occur. Potential bycatch hotspots based on suitable habitat were predicted for cusk Brosme brosme incidentally caught in the Gulf of Maine American lobster Homarus americanus fishery. Data from multiple fisheries-independent surveys were combined in a delta-generalized linear mixed model to generate spatially explicit density estimates for use in an independent habitat suitability index. The habitat suitability indices for American lobster and cusk were then compared to predict potential bycatch hotspot locations. Suitable habitat for American lobster has increased between 1980 and 2013 while suitable habitat for cusk decreased throughout most of the Gulf of Maine, except for Georges Basin and the Great South Channel. The proportion of overlap in suitable habitat varied interannually but decreased slightly in the spring and remained relatively stable in the fall over the time series. As Gulf of Maine temperatures continue to increase, the interactions between American lobster and cusk are predicted to decline as cusk habitat continues to constrict. This framework can contribute to fisheries managers’ understanding of changes in habitat overlap as climate conditions continue to change and alter where bycatch interactions could occur.

Integrating Visual and Bayesian Statistical Analyses in Single Case Experimental Research to Evaluate the Effectiveness and Magnitude of a Comprehensive Behavioral Intervention

2018 ◽  
Author(s):  
Prathiba Natesan ◽  
Smita Mehta
Keyword(s):  
Behavioral Intervention ◽  
Effect Size ◽  
Rate Ratio ◽  
Visual Analysis ◽  
Single Case ◽  
Small Sample ◽  
Statistical Analyses ◽  
Data Types ◽  
Ratio Effect ◽  
Small Sample Sizes

Single case experimental designs (SCEDs) have become an indispensable methodology where randomized control trials may be impossible or even inappropriate. However, the nature of SCED data presents challenges for both visual and statistical analyses. Small sample sizes, autocorrelations, data types, and design types render many parametric statistical analyses and maximum likelihood approaches ineffective. The presence of autocorrelation decreases interrater reliability in visual analysis. The purpose of the present study is to demonstrate a newly developed model called the Bayesian unknown change-point (BUCP) model which overcomes all the above-mentioned data analytic challenges. This is the first study to formulate and demonstrate rate ratio effect size for autocorrelated data, which has remained an open question in SCED research until now. This expository study also compares and contrasts the results from BUCP model with visual analysis, and rate ratio effect size with nonoverlap of all pairs (NAP) effect size. Data from a comprehensive behavioral intervention are used for the demonstration.

No Evidence that Experiencing Physical Warmth Promotes Interpersonal Warmth: Two Failures to Replicate Williams and Bargh (2008)

2018 ◽  
Author(s):  
Christopher Chabris ◽  
Patrick Ryan Heck ◽  
Jaclyn Mandart ◽  
Daniel Jacob Benjamin ◽  
Daniel J. Simons
Keyword(s):  
Null Hypothesis ◽  
Small Sample ◽  
Sample Sizes ◽  
Double Blind ◽  
Bayesian Analyses ◽  
Physical Warmth ◽  
Small Sample Sizes ◽  
Interpersonal Warmth

Williams and Bargh (2008) reported that holding a hot cup of coffee caused participants to judge a person’s personality as warmer, and that holding a therapeutic heat pad caused participants to choose rewards for other people rather than for themselves. These experiments featured large effects (r = .28 and .31), small sample sizes (41 and 53 participants), and barely statistically significant results. We attempted to replicate both experiments in field settings with more than triple the sample sizes (128 and 177) and double-blind procedures, but found near-zero effects (r = –.03 and .02). In both cases, Bayesian analyses suggest there is substantially more evidence for the null hypothesis of no effect than for the original physical warmth priming hypothesis.

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