The patterns of variations in fisheries time series are known to result from a complex combination of species and fisheries dynamics all coupled with environmental forcing (including climate, trophic interactions, etc.). Disentangling the relative effects of these factors has been a major goal of fisheries science for both conceptual and management reasons. By examining the variability of 169 tuna and billfish time series of catch and catch per unit effort (CPUE) throughout the Atlantic as well as their linkage to the North Atlantic Oscillation (NAO), we find that the importance of these factors differed according to the spatial scale. At the scale of the entire Atlantic the patterns of variations are primarily spatially structured, whereas at a more regional scale the patterns of variations were primarily related to the fishing gear. Furthermore, the NAO appeared to also structure the patterns of variations of tuna time series, especially over the North Atlantic. We conclude that the patterns of variations in fisheries time series of tuna and billfish only poorly reflect the underlying dynamics of these fish populations; they appear to be shaped by several successive embedded processes, each interacting with each other. Our results emphasize the necessity for scientific data when investigating the population dynamics of large pelagic fishes, because CPUE fluctuations are not directly attributable to change in species' abundance.Atlantic tuna ͉ North Atlantic Oscillation ͉ time-series analysis F ish stocks are highly variable in size at most time scales (i.e., from the short-term to the long-term) (1, 2). Understanding the underlying mechanisms of such variations has been of focal interest during the past century (3) for both conceptual and management perspectives. On one hand we now know that fish populations are affected by a broad spectrum of environmental factors, be it biotic or abiotic. However, on the other hand it is now widely accepted that fishing activity cannot be reduced to a simple removal of individuals, because such removals profoundly modify the population demography and structure and alter species and trophic interactions (4-8).Time series of commercial catch contain (as is generally the case for most ecological time series) noisy and mixed information on the respective effects of climate variability, environmental forcing, population dynamics, and exploitation. Disentangling the relative effects of the many factors affecting the dynamics of populations has been considered to be the ultimate target of fisheries science. Recent work, however, has demonstrated that such effects are not simply additive, but rather do interact (9-12). Analyzing the patterns of variations of different fish species, in contrasting environments and subject to a variety of fishing pressures, is, thus, expected to shed light on the relative effects of these factors and/or the way they interact.As part of this study we have examined an original and extensive data set of 169 time series, composed with 75 catch per unit ef...

Present address: SPC Headquarters, BP D5, 98848 Noumea Cedex, 95 Promenade Roger Laroque, Anse Vata, New Caledonia ABSTRACT: Atlantic cod Gadus morhua stomach contents (n = 30 973, including 28 377 non-empty stomachs) and morphometric measurements on live snow crab Chionoecetes opilio and cod were examined to assess the predator-prey relationship between these 2 species. The most common snow crab instars found in cod stomachs were III and V (~6 to 8 and ~12 to 16 mm carapace width [CW], respectively) in the northern Gulf of St. Lawrence (GSL) and VI and VII (~17 to 23 and ~23 to 31 mm CW, respectively) in the southern GSL. A significant positive relationship was found between cod length and the largest and smallest CW of snow crab ingested by cod. Positive relationships were also found between gape width and body length in cod and between 3 measures of size (maximum span, width at rest, length at rest) and CW in snow crab. Snow crab length at rest was closely related to cod gape width, suggesting that the largest snow crab ingested by cod must be attacked from the side. There appears to be a plateau at 65.1 mm in the relationship between maximum snow crab CW and cod length, caused by the absence of large (adolescent and adult) male snow crab in cod stomachs. Other studies have found recently moulted, soft-shell snow crabs in cod stomachs, but this appears to be rare. Thus, snow crabs are susceptible to predation by cod mostly for the first 4 yr of postsettlement in the GSL. Any effect of cod predation on the snowcrab fishery would be felt 6 to 11 yr later, given growth models established for the GSL. KEY WORDS: Chionoecetes opilio · Gadus morhua · Gape width · Prey selection Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 363: [227][228][229][230][231][232][233][234][235][236][237][238][239][240] 2008 instance, snow crabs are stenothermic and are found in greatest numbers at bottom-water temperatures between -1 and 4°C (Slizkin 1982, Squires 1990). Therefore, changes in water temperature are likely to result in changes in crab abundance and habitat range (Tremblay 1997, Sainte-Marie & Gilbert 1998, Orensanz et al. 2004. Interactions between climate and physical oceanography can also influence food supply as well as larval production, distribution and survival (Rosenkranz et al. 2001, Zheng & Kruse 2006.Many authors have proposed that predation can also influence distribution and abundance of snow crab. It has been hypothesized that cod (Gadus morhua in the Atlantic, G. macrocephalus in the Pacific) can regulate snow crab populations (Bailey 1982, Tremblay 1997, Orensanz et al. 2004. Two studies suggest the increase in the biomass and geographic range of snow crab observed in the 1990s in eastern Canada was due to the collapse of Atlantic cod stocks, which was presumed to result in a major reduction in total predation mortality for the snow crab populations (Worm & Myers 2003. However, studies based solely on correlations are insufficient to demonstrate top-down ...

Relationships between albacore tuna (Thunnus alalunga) longline catch per unit effort (CPUE) and environmental variables from model outputs in New Caledonia's Exclusive Economic Zone (EEZ) were examined through generalized linear models at a 1°s patial resolution and 10-day temporal resolution. At a regional (EEZ) scale, the study demonstrated that a large part of albacore CPUE variability can be explained by seasonal, interannual and spatial variation of the habitat. Results of the generalized linear models indicated that catch rates are higher than average in the northwestern part of the EEZ at the beginning of the year (January) and during the second half of the year (July-December). In the northwestern region of the EEZ, high CPUEs are associated with waters <20.5°in the intermediate layer and with moderate values of primary production. Longline CPUE also appeared to be dependent on prey densities, as predicted from a micronekton model. Albacore CPUE was highest at moderate densities of prey in the epipelagic layer during the night and for relatively low prey densities in the mesopelagic layer during the day. We also demonstrated that the highest CPUEs were recorded from 1986 to 1998, which corresponds to a period with frequent El Niño events.

Purpose: In this longitudinal study, a group of school children with Down syndrome (DS) and reduced accommodation were prescribed bifocals and followed to investigate the impact of bifocal spectacles on early literacy and visual perceptual skills. The natural progression of early literacy skills in this population along with the changes with bifocals, described by monthly subtest scores and the time taken to complete literacy and visual perceptual tasks, are reported. Methods: Fourteen children with DS, aged eight to 18 years, were followed for five months with single vision lenses; 11 were prescribed bifocals based on their accommodative ability and followed for another five months. A battery of reading and visual perceptual tests was administered before and after prescription of bifocals. Monthly subtests of similar tasks were administered to measure progress. All the visits were videotaped to determine the time taken for the child to complete each task. Results: There was no significant measurable natural progression of early literacy skills in this group of participants on the Word Identification (WI) subtest (Repeated Measures ANOVA, F [4, 24] =1.377, p = 0.271) and Dolch sight words (RMANOVA F [4, 24] = 0.344, p = 0.846). In contrast, once bifocals were prescribed there was significant improvement in the scores of the monthly subtests (p = 0.050, 0.025 and 0.023 for WI, Dolch sight words and numbers, respectively) and the rate of progress in monthly scores improved for WI (p = 0.008). Repeated measures Analysis of Variance showed a significant decrease in the completion times with bifocals for the WI test in the full battery of tests (p = 0.0015). There was significant correlation between the improvement in focus with bifocals and the decrease in completion time for the WI task (p = 0.004). Conclusions: This study demonstrates no significant natural progression over a fivemonth period in the group of participants with Down syndrome; however, with bifocals, faster and improved performance on some literacy skills was observed. We recommend that bifocals be considered in children with Down syndrome presenting with inadequate accommodation to optimise their educational potential.

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