Estimate Movement Rates Research Articles

Extensive daily movement rates measured in territorial arctic foxes.

An animal's movement rate is a central metric of movement ecology as it correlates with its energy acquisition and expenditure. Obtaining accurate estimates of movement rate is challenging, especially in small highly mobile species where GPS battery size limits fix frequency, and geolocation technology limits positions’ precision. In this study, we used high GPS fix frequencies to evaluate movement rates in eight territorial arctic foxes on Bylot Island (Nunavut, Canada) in July–August 2018. We also assessed the effects of fix interval and location error on estimated movement rates. We obtained 96 fox‐days of data with a fix interval of 4 min and 12 fox‐days with an interval of 30 s. We subsampled the latter dataset to simulate six longer fix intervals ranging from 1 to 60 min and estimated daily distances traveled by adding linear distances between successive locations. When estimated with a fix interval of 4 min, daily distances traveled by arctic foxes averaged 51.9 ± 11.7 km and reached 76.5 km. GPS location error averaged 11 m. Daily distances estimated at fix intervals longer than 4 min were greatly underestimated as fix intervals increased, because of linear estimation of tortuous movements. Conversely, daily distances estimated at fix intervals as small as 30 s were likely overestimated due to location error. To our knowledge, no other territorial terrestrial carnivore was shown to routinely travel daily distances as large as those observed here for arctic foxes. Our results generate new hypotheses and research directions regarding the foraging ecology of highly mobile predators. Furthermore, our empirical assessment of the effects of fix interval and location error on estimated movement rates can guide the design and interpretation of future studies on the movement ecology of small opportunistic foragers.

Least‐cost path analysis for urban greenways planning: A test with moths and birds across two habitats and two cities

Abstract One of the major planning tools to respond to urban landscape fragmentation is the development of ecological corridors, that is, interconnected networks of urban green and blue spaces. Least‐cost paths (LCP) appear to be an easy and appropriate resistance‐based modelling method to respond to urban planners’ needs. However, the ecological validation of urban corridors using LCP is rarely performed and needs to be generalized to different species, habitats and cities. We developed an experimental design to test the efficiency of LCP predictions to detect highly connecting landscape contexts that facilitate individual movements compared to movements in less connecting landscape contexts. We deliberately assigned LCP analysis parameters based on the scientific literature and expert knowledge to test a method potentially easy to use for urban stakeholders. To extend the validation, we applied our LCP model to two biological taxa with different habitat requirements: grassland‐dwelling moths and forest‐dwelling passerines, and to two medium‐sized cities. We used mark–release–recapture (MRR) methods for moths and playback recall protocols for passerines to compare the patterns of individual movement between two contrasted connectivity contexts determined by the presence and absence of modelled LCPs. MRR protocol estimated movement rates between herbaceous patches and the two contrasted connectivity contexts. Playback recall protocol consisted in attracting individuals from wooded patches to the two contrasted connectivity contexts. A movement was considered facilitated, when displacement was rapidly engaged and individuals moved a long distance from their wooded patch. Moth and passerine movement patterns differed between the two connectivity contexts: moth recapture rates were higher in highly connecting contexts than in less connecting contexts. For passerine birds, responses to playback recalls were faster and movement distance longer in highly connecting contexts. All results support the hypothesis that both taxa were more prone to move in corridors modelled by LCP. Synthesis and applications. The convergence of the results for different biological models and across cities strengthens the relevance of LCP analysis for planning urban greenways and provides guidelines for landscape planners in the development of these corridors to favour the movement and survival of multiple urban species.

Using the Active Faults of Eurasia Database for solving tectonic problems

The article describes principles, methods and tasks of tectonic studies using computer processing of the Active Faults of Eurasia Database. This new database contains more than 30000 objects that are geographically linked, equipped with attributes of the kinematic type, estimated movement rates and activity confidence ranks. As an exam‐ ple, we consider processing of the data on several tectonic regions of the Alpine‐Himalayan mobile belt and construction of rose‐diagrams of faults for a comparative analysis of their Late Cenozoic kinematics. The processed data set also covered the Caucasus‐Anatolian region and the entire central part of the mobile belt, and fields of shortening/lengthening and shearing were mapped to assess the patterns of these processes in different areas and to determine the characteristics of the tectonic flow of the upper crust material. Prospects are discussed for the database processing with the use of all the available attributive information for structural‐kinematic and geodynamic analysis, including processing of the database in combination with independent remote and geophysical data.

Movements of Atlantic halibut in the Gulf of Maine based on geolocation

AbstractAtlantic halibut are a “Species of Concern” in US waters and little is known about their movements and stock structure. Recent stock assessments drew attention to the paucity of information for assessing and managing this stock. To investigate movement patterns and stock structure, halibut were tagged off Massachusetts and Maine within US waters of the Gulf of Maine region using pop-up satellite archival tags and data storage tags. A hidden Markov model (HMM) geolocation method previously developed for other groundfish species was adapted to estimate the movement tracks of the tagged halibut (n = 25) based on the tag-recorded depth and temperature. Total distance travelled based on geolocation ranged from 36 to 1701 km, whereas straight line distance between tagging and end locations ranged from 0.4 to 440.7 km. Estimated movement rates varied between 2.7 and 10 km day−1. Two tagged halibut made long-distance movements to putative spawning habitat in the Northeast Channel off Georges Bank. Thirteen (13) out of 25 geolocated individuals were estimated to have reached Canadian waters. Geolocation results revealed home range, return movement, and seasonal migration movement patterns exhibited by the tagged halibut. The HMM geolocation method could be a useful tool in providing information on halibut movements that can inform stock assessment and management decisions.

Effects of post‐release movements on survival of translocated sage‐grouse

ABSTRACTTranslocation is a vital tool in conservation and recovery programs, and knowledge of factors that determine demographic rates of translocated organisms is important for assessing the efficacy of translocations. Greater sage‐grouse (Centrocercus urophasianus) have been the subject of recent translocation efforts because of their declining range and their usefulness as an umbrella species for conservation. Using a long‐term data set on sage‐grouse in central Washington, USA, we compared movement and demographic rates of translocated and resident birds. Because newly translocated birds experience physiological stress during translocation and are released in unfamiliar habitat, we hypothesized their demographic rates would differ from residents. We analyzed 18 years of radio‐tracking data acquired from resident, newly translocated (<1 yr post‐translocation; T1), and previously translocated (>1 yr post‐translocation; T2) sage‐grouse between 1989 and 2017 to estimate movement rates, survival, and productivity. Newly translocated sage‐grouse exhibited farther daily movements (0.58 km/day) and smaller 95% home ranges (89 km2) than residents and previously translocated birds. Daily movements and sex influenced survival, but survival did not differ according to residency status. Furthermore, birds that survived to a second year after translocation exhibited shorter daily movements compared to their first year ( = −0.727 ± 0.157 [SE]), which corresponded with increased survival the second year (T1 = 0.526, T2 = 0.610). This decrease in movements and increase in survival the second year was not apparent in the control group of resident birds, indicating a possible behavioral link to survival of newly translocated sage‐grouse. Most productivity metrics were similar for translocated and resident birds, except for nest propensity (i.e., nest initiation rate), which was lower for newly translocated birds (35%) compared to residents and previously translocated birds. Our results reveal that translocated sage‐grouse exhibit temporary differences in some demographic parameters in their first year, which later align with those of resident birds in subsequent years. Similarities in adult and nest survival according to residency status further suggest that translocation may prove to be a viable tool for restoring and conserving this species. Continued declines in sage‐grouse populations in Washington, however, indicate that habitat conversion and fragmentation may be reducing demographic rates of residents and translocated birds, which warrants further study. © 2019 The Wildlife Society.

Multi-state dead recovery mark-recovery model performance for estimating movement and mortality rates

Multi-state mark-recovery models are used to estimate movement and mortality rates of terrestrial and aquatic animals. These models have become especially popular in the last 20 years since technology and statistical techniques have improved to accommodate the extensive data requirements. However, the ability of multi-state mark-recovery models to estimate movement rates has received little evaluation, with few studies exploring the effects of alternative release and recovery designs on the bias and precision of estimates. Our objectives were to evaluate the effects of the spatio-temporal pattern of releases, pattern of recovery efforts, and number of releases on the performance of a multi-state mark-recovery model. We generated mark-recovery data from a spatial model and fitted them using a multi-state dead recovery model that included prior distributions on movement rates, natural mortality, and catchability. We generated data using a spatially variable schedule of releases and effort, and a release size of about 1 million individuals to mimic a mark-recovery study conducted for Atlantic Menhaden Brevoortia tyrannus in the late 1960s. We also ran alternative scenarios of sample size and spatially uniform releases and effort, either by themselves or in combination to determine their effects on the accuracy of the estimates. The model generally produced unbiased estimates of mortality rates with median error < 0.02 yr−1 for all scenarios, but some biases were present for the movement rates. Movement rates and catchability were more accurately and precisely estimated in scenarios that included spatially uniform fishing effort, while spatially uniform releases had little to no effect on bias or precision of estimated movement rates. Increased sample size improved accuracy of all parameter estimates except for the lowest movement rates. Future mark-recovery experiments that use a multi-state dead recovery model may benefit from distributing recovery effort uniformly over time and space.

Simulation testing the robustness of a multiregion, tag-integrated assessment model that exhibits natal homing and estimates natural mortality and reporting rate

The influence of model complexity on integrated tagging and catch-at-age analysis (ITCAAN) parameter estimation is poorly understood for populations exhibiting natal homing. We investigated ITCAAN performance under varying levels of movement, degree of similarity in population productivities, data quality, spatial complexity in parameterization, and whether natural mortality and (or) reporting rates were fixed at actual values, estimated, or misspecified. Dynamics of four populations with natal homing that intermixed during periods of harvest were simulated based on Lake Erie walleye (Sander vitreus). Our results suggest, when high-quality tagging data are available, ITCAAN models are able to simultaneously estimate movement rates, natural mortality, and tag reporting rates, though accuracy and precision of model estimates will decrease with greater model complexity and fewer tags released. Additionally, ITCAAN models may have difficulty estimating individual population abundances under certain movement rates when population productivities are vastly different. ITCAAN models that estimate natural mortality and reporting rates may perform best with similar sized populations and when data are available to assist the estimation of reporting rates.

Can we predict the expansion rate of a translocated butterfly population based on a priori estimated movement rates?

Conservation translocation is a controversial, yet sometimes the only applicable, conservation tool in the face of the human-induced environmental change. One important aspect often neglected in translocation experiments is predicting the spatial expansion potential of the translocated population in the release area. In this study, we used a spatially explicit movement model to project the expansion rate of a translocated clouded Apollo (Parnassius mnemosyne) population. The model was parameterised with data collected from the source population inhabiting an open landscape with well-connected habitat patches. We then used these parameter estimates to simulate the spread of the translocated population in the new area, which was a forested landscape with more fragmented habitat. We tested the model predictions by comparing them to the observed expansion rate between 2000 and 2016. Additionally, we tested whether including annually varying weather conditions would increase realism in the projections. Model predictions were qualitatively correct and quantitatively most accurate for flight seasons with prevailing weather conditions similar to those of the season when the data for parameter estimation was collected. We conclude that spatially explicit movement models are potential tools to improve the planning of future conservation translocations in terms of choosing the optimal release area, as they enable the comparison of functional connectivities even between structurally different landscapes. However, our results suggest that a model fitted based on movement data from a single year may not be representative for the overall dispersal rates due to temporal variation in dispersal.

Using spatio‐temporal models of population growth and movement to monitor overlap between human impacts and fish populations

Summary Protected and managed species, including harvested fishes, exhibit spatial and temporal variation in their distribution and productivity. Spatio‐temporal variation can arise from differences in habitat quality, human impacts (including harvest), density‐dependent changes in per capita productivity, as well as individual movement. Human impacts (e.g. direct harvest) also vary spatially and over time, and monitoring the overlap between impacts and population distribution is necessary to ensure that human impacts are sustainable and to prioritize research and management for populations that are heavily impacted. However, estimating spatio‐temporal variation in human impacts and population dynamics while accounting for individual movement has remained computationally challenging for decades. We developed a spatial population growth (also known as ‘surplus production’) model that is inspired by finite element analysis, which estimates spatio‐temporal population dynamics given density‐dependent population regulation, individual movement and spatially explicit harvest. We demonstrate the method using data for big skate Raja binoculata in the California Current from 2003 to 2013 and demonstrate that results can be processed to estimate an upper limit on sustainable harvest (an ‘overfishing limit’). We also conduct a simulation experiment to explore the small‐sample properties of parameter estimates. A simulation experiment confirms that real‐world sample sizes are sufficient to estimate the sustainable harvest level within 20% of its actual value. However, sample sizes are likely insufficient to reliably estimate movement rates. The spatial population growth model estimates an overfishing limit of 740–890 metric tonnes for big skate from 2010 to 2013, compared with annual harvest &lt;100 tonnes. This suggests that recent harvest of big skate is likely sustainable, and sensitivity analysis confirms that this conclusion is robust to different potential rates for individual movement. Synthesis and applications. We recommend that spatio‐temporal population models be used across systems and taxa to monitor the spatial overlap between species distribution and human impacts. For big skate, we recommend management rules triggering additional data collection and assessment effort if harvest rates substantially increase. We also recommend future research regarding spatial management regulations for emerging fisheries.

Lek fidelity and movement among leks by male Greater Sage‐grouse Centrocercus urophasianus: a capture‐mark‐recapture approach

Males in lek mating systems tend to exhibit high fidelity to breeding leks despite substantial evidence of skewed mating success among males. Although movements between leks are often reported to be rare, such movements provide a mechanism for an individual to improve lifetime fitness in response to heterogeneity in reproductive conditions. Additionally, estimates of apparent movements among leks are potentially biased due to unaccounted variation in detection probability across time and space. We monitored breeding male Greater Sage‐grouse Centrocercus urophasianus on 13 leks in eastern Nevada over a 10‐year period, and estimated movement rates among leks using capture‐mark‐recapture methods. We expected that male movement rates among leks would be low, despite predictions of low breeding success for most males, and that detection rates would be highly variable among leks and years. We used a robust design multistate analysis in Program mark to estimate probability of movements among leks, while accounting for imperfect detection of males. Male Sage‐grouse were extremely faithful to their leks; the annual probability of a male moving away from its original lek of capture was approximately 3% (se = 0.01). Detection probabilities varied substantially among leks (range = 0.21–0.95), and among years (range = 0.30–0.76), but remained relatively constant within years at each lek. These results suggest that male Sage‐grouse dispersal is either rare, or consists primarily of dispersal of sub‐adults from their natal areas prior to the breeding season. The study highlights the benefits of robust design multistate models over standard ‘live‐encounter’ analyses, as they not only permit estimation of additional parameters, such as movement rates, but also allow for more precise parameter estimates that are less sensitive to heterogeneity in detection rates. Additionally, as these data were collected using capture‐mark‐recapture methods, our approach to estimating movement rates would be beneficial in systems where radiotagging is detrimental to the study organism.

Estimating dispersal among numerous sites using capture-recapture data.

Dispersal affects processes as diverse as habitat selection, population growth, and gene flow. Inference about dispersal and its variation is thus crucial for assessing population and evolutionary dynamics. Two approaches are generally used to estimate dispersal in free-ranging animals. First, multisite capture-recapture models estimate movement rates among sites while accounting for survival and detection probabilities. This approach, however, is limited in the number of sites that can be considered. Second, diffusion models estimate movements within discrete habitat using a diffusion coefficient, resulting in a continuous processing of space. However, this approach has been rarely used because of its mathematical and implementation complexity. Here, we develop a multi-event capture-recapture approach that circumvents the issue of too many sites while being relatively simple to be implemented in existing software. Moreover, this new approach allows the quantifying of memory effects, whereby the decision of dispersing or not on a given year impacts the survival or dispersal likelihood of the following year. We illustrate our approach using a long-term data set on the breeding ecology of a declining passerine in southern Quebec, Canada, the Tree Swallow (Tachycineta bicolor).

Use of multiple selectivity patterns as a proxy for spatial structure

There is widespread recognition that spatial structure is important for fisheries stock assessment, and several efforts have been made to incorporate spatial structure into assessment models. However, most studies exploring the impact of ignoring spatial structure in stock assessments have developed population models with multiple subpopulations, rather than exploring the impact spatial dynamics may have on performance of non-spatially structured assessment methods. Furthermore, the data available for stock assessments usually do not include tagging or other data necessary to estimate movement rates. One solution to this problem is to include several fleets, each with a different selectivity pattern to represent availability, within a spatially-aggregated assessment method. In this study, the impacts of ignoring spatial structure, and the effectiveness of using multiple selectivity patterns as a proxy for spatial structure, are evaluated for the northern subpopulation of Pacific sardine (or California sardine; Sardinops sagax). A spatially-explicit operating model is used to explore three spatial factors: the existence of size-dependent seasonal migrations across large geographical areas, the influx of another stock into the area of the assessed stock, and the occurrence of recruitment outside the area where it is assumed to occur. Two other factors related to data were evaluated: data availability and data collection design. The assessment model (AM) is based on the 2010 stock assessment for Pacific sardine, implemented in Stock Synthesis, and includes two seasons per year and six fleets, each with a different selectivity pattern. Ignoring spatial structure is found to negatively impact estimation performance, with seasonal movement having the largest impact. The AM compensates for ignoring movement and spatial structure by adjusting the selectivity patterns, but selectivity alone is not able to account for all biases caused by spatial structure.

Integrating recapture-conditioned movement estimation into spatial stock assessment: A South Australian lobster fishery application

The practical aim of this study was to estimate biomass in two subregions, inshore (<60 m depth) and offshore (>60 m), for application to rock lobster management. To account for lobster movement between these subregions, movement estimation was integrated into the length-structured stock assessment model. Tagged lobsters were released inshore and offshore in the mid-1990s. For fitting to these conventional single tag-recoveries, a recapture-conditioned movement rate estimation method was adapted and integrated into the assessment model. The individually-tailored probabilities of survival during time-at-large and of subsequent capture in each subregion needed to estimate movement rates are provided by the over-arching stock assessment estimator. Calculating a probability specific for each lobster recapture permits the estimator to account for naturally varying times and locations of tag release and recapture. Seasonality of tagged lobster movements indicated that inshore-to-offshore migration occurred predominantly in winter. Yearly movement rates of lobsters were relatively low. Biomass was approximately 3–4 times higher inshore than offshore. Testing using simulated data confirmed the accuracy of model-integrated recapture-conditioned movement estimates. Using these same simulated data, conventional movement rate estimates, calculated as raw proportions of recaptured lobsters that moved, were positively biased. Incorporating survival and recovery rates in movement estimation can thus substantially improve the accuracy of movement, and thus biomass, estimates in spatially-resolved stock assessments.

A Bayesian mark–recapture model for multiple-recapture data in a catch-and-release fishery

This paper extends a state–space Bayesian mark–recapture framework to multiple-recapture data to estimate fishery-specific capture and mortality rates and seasonal movement rates for fish in different length classes. The methodology is applied to tag recapture data for white sturgeon ( Acipenser transmontanus ) collected in the recreational fishery and the Canadian Department of Fisheries and Ocean’s test fishery at Albion in the lower Fraser River. Significant differences were found between some estimated movement rates by season and length class, supporting the notion of there being marked differences in seasonal movement patterns between different life history stages of A. transmontanus in the lower Fraser River. Uncertainty in the tag reporting rate parameter, quantified using a recreational creel sampling program, is summarized by a prior distribution. The utility of recreational fishing effort as a model covariate in accounting for seasonal and spatial variation in recapture rates is addressed using Bayesian model evaluation criteria. The data provide strong support in favour of models that include fishing effort as a covariate. The appropriate level of stratification for the recreational catchability parameter q is assessed using Bayesian model evaluation criteria; models in which q is estimated by season and length class have the highest posterior probabilities.

Estimating rates of fish movement from tag recoveries: conditioning by recapture

Tag-recovery data are commonly used to estimate movement rates of fish stocks. Fishers report tagged fish found in their catch; however, not all recoveries are reported to fishery researchers and the rate of nonreporting is usually not known or is imprecisely estimated. To obviate the problem of nonreporting, an estimator of movement rates is proposed that does not use the number originally tagged but is fitted to the relative proportions recaptured in each cell in each time step subsequent to release. Rates of processes that occur in the tag-release spatial cell, such as short-term tagging mortality and survival, cancel from the predicted likelihood probabilities. Similarly, rates in the recapture cell for processes of ongoing tag loss, natural mortality, and tag nonreporting, if they can be reasonably approximated as uniform across cells, also cancel. Estimators are presented assuming one of two levels of auxiliary fishery inputs: (i) total mortality by cell or time step, or (ii) if mortality can be approximated as spatially uniform, effort totals in each cell, by time step. Yearly movement transition matrices were estimated for King George whiting (Sillaginodes punctata) in South Australia among 11 spatial cells from tag recoveries gathered over a period of three decades.

ANALYSIS OF ANIMAL MOVEMENT USING OPPORTUNISTIC INDIVIDUAL IDENTIFICATIONS: APPLICATION TO SPERM WHALES

Data sets in which animals are identified individually in different places and times may contain considerable information on movements. However; if the probability that an animal is reidentified depends on its movement pattern, then standard methods of analyzing movement are not applicable. I show that modifications of maximum likelihood methods, in which the identifications themselves establish the spatial and temporal distri- bution of effort, can be used to derive movement parameters in three situations: (1) Iden- tifications in one location allow calculation of the identification rate (the prob- ability of reidentification after various time lags) as well as estimation of residence times inside, and outside, the study area. (2) When more than one study area is sampled, it is possible to derive lagged identification rates between them and to estimate movement rates between areas and other population parameters. (3) Movements through continuous space can be described by diffusion rates (rates of population spread), and plots of squared displacement against time lag. To simplify computation, and to permit the analysis of large data sets, summed nonindependent log-likelihoods can be maximized in place of the true log-likelihood to obtain approximately unbiased parameter estimates, and binomial, mul- tinomial, or hypergeometric models can be approximated by the Poisson distribution. The first and third of the techniques were verified using simulated data, and all were applied to a 13-yr data set of identifications of sperm whales in the South Pacific Ocean. Residence times in waters close to the Galapagos Islands were of the order of 8 d, but during the study period there was a substantial net movement out of the Galapagos region and into waters of the coastal eastern tropical Pacific. Diffusion rates of sperm whales were -700 km2/d over time scales from 1 to 100 d but decreased considerably over time scales of years, indicating displacements of -50 km/d within home ranges spanning -1000 km. Although giving relatively imprecise estimates of movement parameters compared to more standard methods, the techniques considered here should be particularly useful when ex- amining animal movements over long time scales.

Analysis of Animal Movement Using Opportunistic Individual Identifications: Application to Sperm Whales

Data sets in which animals are identified individually in different places and times may contain considerable information on movements. However, if the probability that an animal is reidentified depends on its movement pattern, then standard methods of analyzing movement are not applicable. I show that modifications of maximum likelihood methods, in which the identifications themselves establish the spatial and temporal distribution of effort, can be used to derive movement parameters in three situations: (1) Identifications in one location allow calculation of the “lagged identification rate” (the probability of reidentification after various time lags) as well as estimation of residence times inside, and outside, the study area. (2) When more than one study area is sampled, it is possible to derive lagged identification rates between them and to estimate movement rates between areas and other population parameters. (3) Movements through continuous space can be described by diffusion rates (rates of population spread), and plots of squared displacement against time lag. To simplify computation, and to permit the analysis of large data sets, summed nonindependent log-likelihoods can be maximized in place of the true log-likelihood to obtain approximately unbiased parameter estimates, and binomial, multinomial, or hypergeometric models can be approximated by the Poisson distribution. The first and third of the techniques were verified using simulated data, and all were applied to a 13-yr data set of identifications of sperm whales in the South Pacific Ocean. Residence times in waters close to the Galápagos Islands were of the order of 8 d, but during the study period there was a substantial net movement out of the Galápagos region and into waters of the coastal eastern tropical Pacific. Diffusion rates of sperm whales were ∼700 km2/d over time scales from 1 to 100 d but decreased considerably over time scales of years, indicating displacements of ∼50 km/d within home ranges spanning ∼1000 km. Although giving relatively imprecise estimates of movement parameters compared to more standard methods, the techniques considered here should be particularly useful when examining animal movements over long time scales.

Searching and Feeding Behavior ofNephaspis oculatusandDelphastus catalinae(Coleoptera: Coccinellidae), Predators ofBemisia argentifolii(Homoptera: Aleyrodidae)

The coccinellids Nephaspis oculatus (Blatchley) and Delphastus catalinae (LeConte) [formerly D. pusillus (LeConte)] are predators of whiteflies (Homoptera: Aleyrodidae), and have shown potential for biological control of Bemisia argentifolii Bellows & Perring in greenhouses. We observed the searching and feeding behavior of N. oculatus and D. catalinae on hibiscus ( Hibiscus rosa-sinensis L.). D. catalinae larvae maintained the entire body in contact with the substrate while moving, whereas N. oculatus larvae planted the uropod on the substrate and swept the body in an arc while searching. Estimated movement rates of all stages of D. catalinae were greater than the corresponding stages of N. oculatus. However, the searching areas by different larval stages of D. catalinae were significantly smaller than those by the corresponding larval stages of N. oculatus, which the larvae sweep around while searching. The adults of both coccinellid species traveled in a similar pattern; therefore, D. catalinae, moving at a greater rate, searched a greater area than that of N. oculatus, moving at a slower rate. Larvae and adults of both coccinellid species responded to prey only after contacting prey with their mouthparts or front legs. Younger larvae took significantly longer to consume prey than older larvae or adults. Larvae and adults of the smaller N. oculatus consumed whiteflies at a significantly slower rate than did corresponding stages of D. catalinae.

Movement, Mortality, and Size Selectivity of Sport- and Trawl-Caught Lingcod off Washington

Abstract Movement, size selectivity, and fishing mortality parameters of lingcod Ophiodon elongatus were estimated for the sport and trawl fisheries off Washington by using mark–recapture data from 1991 to 1994. Parameters were estimated with a multiple-year tag release sample design by maximizing the likelihood of the observed tag recoveries via the method of tuned simulation. The results confirm the open nature of the coastal lingcod population: lingcod found near shore became vulnerable to the trawl fishery off shore, though very few lingcod found off shore became vulnerable to the sport fishery near shore. The relatively greater selectivity of small female lingcod estimated by this study, compared with estimates from a previous catch-at-age analysis, suggests the possibility of undocumented discard mortality in the trawl fishery. Previous mark–recapture fishery interaction studies required independent estimates of fishing mortality to estimate movement rates. This study shows that both fishing mortali...