Outmigration survival of acoustic-tagged, hatchery-origin, late-fall-run Chinook salmon (Oncorhynchus tshawytscha) smolts from the Sacramento River was estimated for 5 years (2007–2011) using a ...receiver array spanning the entire outmigration corridor, from the upper river, through the estuary, and into the coastal ocean. The first 4 years of releases occurred during below-average river flows, while the fifth year (2011) occurred during above-average flows. In 2011, overall outmigration survival was two to five times higher than survival in the other 4 years. Regional survival estimates indicate that most of the improved survival seen in 2011 occurred in the riverine reaches of the outmigration corridor, while survival in the brackish portions of the estuary did not significantly differ among the 5 years. For the 4 low-flow years combined, survival rate in the river was lower in the less anthropogenically modified upper reaches; however, across all regions, survival rate was lowest in the brackish portion of the estuary. Even in the high-flow year, outmigration survival was substantially lower than yearling Chinook salmon populations in other large rivers. Potential drivers of these patterns are discussed, including channelization, water flow, and predation. Finally, management strategies are suggested to best exploit survival advantages described in this study.
Telemetry is increasingly being used to estimate population-level survival rates. However, these estimates may be affected by the detectability of telemetry tags and are reliant on the assumption ...that telemetry data represent the movements of the tagged fish. Predation on tagged fish has the potential to bias survival estimates, and unlike the issue of detectability, methods to correct for the resulting bias (termed “predation bias”) are not yet developed. In an acoustic telemetry study on inner Bay of Fundy Atlantic salmon (Salmo salar) smolts during 2008 and 2011, unusual tag detection patterns were indicative that some data may have been representative of the movements of predators rather than smolts. To incorporate predation effects into the resulting survival estimates, a suite of 11 summary migration metrics were compared between Atlantic salmon smolts and striped bass (Morone saxatilis). Cluster analyses revealed that 2.4% to 13.6% of tags implanted in smolts exhibited migration patterns more similar to striped bass than to other smolts, which was interpreted here as evidence of predation. Reassigning the fate of these tags as “depredated–died” reduced estimated survival from 43.5% to 41.1% in 2008 and from 32.6% to 19.0% in 2011 relative to a traditional mark–recapture model, illustrating the effect of predation bias in this case study.
Thousands of people become lost in the wilderness each year and search and rescue personnel are called in to search for and to locate people who are lost. Time is critical as the lost person's chance ...of survival decreases over time. One method of improving search outcomes is efficient and accurate planning of search areas. Search and rescue planning techniques have been developed over time through extensive training, experience and knowledge. To expedite the search area planning process, an agent-based model (ABM) was used to highlight probabilistic and evidence-based areas typically considered by search area planners. This model takes spatial data calculated to a timecost raster and incorporates lost person characteristics to determine location-specific probability data that can be used in decisionmaking.
We examined the effect of early marine entry timing and body size on the marine (smolt-to-adult) survival of Puget Sound Chinook salmon (
Oncorhynchus tshawytscha
). We used data from coded wire tag ...release groups of hatchery Chinook salmon to test whether hatchery release date, release size, and size in offshore waters in July and September influenced marine survival. Marine survival was most strongly related to the average body size in July, with larger sizes associated with higher survivals. This relationship was consistent over multiple years (1997-2002), suggesting that mortality after July is strongly size-dependent. Release size and date only slightly improved this relationship, whereas size in September showed little relationship to marine survival. Specifically, fish that experienced the highest marine survivals were released before 25 May and were larger than 17 g (or 120 mm fork length) by July. Our findings highlight the importance of local conditions in Puget Sound (Washington, USA) during the spring and summer, and suggest that declines in marine survival since the 1980s may have been caused by reductions in the quality of feeding and growing conditions during early marine life.
Recent studies have shown that warm temperatures reduce survival of adult migrating sockeye salmon (Oncorhynchus nerka), but knowledge gaps exist on where high-temperature-related mortality occurs ...along the migration and whether females and males are differentially impacted by river temperature. In this study, we monitored 437 radio-tagged Fraser River sockeye salmon and used capture-mark-recapture modelling approaches to investigate whether river thermal conditions differentially influence (i) spatial patterns of survival along a 413-km stretch of migration and (ii) survival of the sexes. Regardless of water temperature, survival decreased in the river section containing the most hydraulically difficult passages of the migration. However, when water temperature was warm (19 °C), survival decreased even further in the final 186 km of the migration prior to reaching the spawning grounds, particularly in females. Female and male survival differed but only when they experienced warm river temperatures. Under such conditions, the overall freshwater migration survival of males was 1.6 times higher (0.79 ± 0.09 standard error, SE) than that of females (0.50 + or - 0.11 SE). As maturing female sockeye salmon maintain higher levels of plasma cortisol compared with males, we suspect that females could be immune- compromised and thus less resistant to pathogens whose rates of development are accelerated by warm temperatures.
The effects of various temperatures on the development and survival of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) and Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) fed on ...Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) were studied, and some biological aspects among these predators were compared. On average, 70 nymphs of R. padi were added to each experimental unit with predator larvae and maintained at 12, 16, 20, 24, 28, or 32°C. The duration (days) and survival (%) were measured for each immature stage of the two predator species. The developmental durations of all H. axyridis larval instars, the total larval stage, the pupal stage and total preimaginal stage were very long at 16°C but shortest at 24°C for the first, second and third larval instars and at 28°C for the fourth larval instar, the total larval stage and the total pre-imaginal stage. Both at 24°C and 28°C, 92% of H. axyridis completed the larva to adult cycle, whereas survival was significantly reduced in the 16 to 20°C range. At the highest temperature (32°C), 70% of H. axyridis did not reach adulthood. In the case of C. externa, the durations of development of all larval instars and the total larval stage became progressively shorter as the temperature increased from 12 to 20°C. At still higher temperatures the developmental duration this insect remained almost constant. The predator completed the larval stage at all temperatures from 12 to 32°C. However, at 12 and 16°C, mortality of the larvae was greater than 88%, and 100% of the pupae perished. Although the lower threshold temperatures estimated for both predator species were very similar, the development period from larva to adult of H. axyridis was only 59% as long as that of C. externa. By comparing certain biological parameters including durations of development and survival rates of the two predator species, it is suggested that H. axyridis has intrinsic advantages over C. externa; however, additional factors must be considered when choosing the species of predator for biological control of R. padi on grass pastures in Brazil. Key Words: predators, aphids, forage, temperature O efeito de varias temperaturas sobre o desenvolvimento e sobrevivencia de Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) e Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) alimentados de Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) foram estudados, assim, como alguns aspectos biologicos entre esses predadores foram comparados. Em media, 70 ninfas de R. padi foi adicionadas em cada unidade experimental, contendo uma larva do predador e foram mantidas a 12, 16, 20, 24, 28, 32°C. Avaliou-se a duragao (dias) e a sobrevivencia (%) de cada instar larval, estagio larval total, estagio pre-pupal, estagio pupal e estagio pre-imaginal dos predadores. A duragao de H. axyridis foi maior a 16°C e reduziu significativamente a 24°C (do primeiro ao terceiro instar) e a 28°C (quarto instar larval, estagio larval total e estagio pre-imaginal). A 24°C e 28°C, 92% dos insetos completaram o ciclo (larva a adulto) havendo redugao significativa a 16 e 20°C. Na maior temperatura estudada (32°C), 70% desse predador nao atingiram a idade adulta. Para C. externa, verificou-se redugao na duragao com incremento da temperatura de 12 a 20°C para todos instares larvais e estagio larval total desse predador. Em temperaturas mais elevadas a velocidade de desenvolvimento do inseto estabilizou-se. O predador completou o estagio larval total em todas as temperaturas testadas. No entanto, houve mortalidade acima de 88% e de 100% das larvas e pupas, respectivamente, a 12 e 16°C. Foi verificado que apesar da temperatura base estimada para ambas especies de predadores terem sido proximas, o periodo de desenvolvimento de larva a adulto de H. axyridis corresponde a 59% daquele de C. externa. Pela comparagao dos parametros biologicos, duragao e sobrevivencia, sugere-se que H. axyridis teve vantagens intrinsecas sobre C. externa, porem, outros fatores devem ser considerados na escolha da especie do predador para o controle biologico de R. padi em forrageiras no Brasil. Palavras-Chave: predador, afideo, forragem, temperatura
Thousands of people become lost in the wilderness each year and search and rescue personnel are called in to search for and to locate people who are lost. Time is critical as the lost person's chance ...of survival decreases over time. One method of improving search outcomes is efficient and accurate planning of search areas. Search and rescue planning techniques have been developed over time through extensive training, experience and knowledge. To expedite the search area planning process, an agent-based model (ABM) was used to highlight probabilistic and evidence-based areas typically considered by search area planners. This model takes spatial data calculated to a timecost raster and incorporates lost person characteristics to determine location-specific probability data that can be used in decisionmaking.
Although studies addressing natural selection have primarily focused on additive genetic effects because of their direct relationship with responses to selection, nonadditive genetic and maternal ...effects can also significantly influence phenotypes. We partitioned the phenotypic variance of survival and fitness-related traits in juvenile Atlantic salmon (Salmo salar) from three allopatric populations (LaHave, Sebago, and Saint-Jean) into additive genetic, nonadditive genetic, and maternal environmental effects using a full-factorial breeding design. We also modelled the potential increase in offspring performance if nonrandom mating (e.g., mate choice) is considered instead of random mating. The three populations exhibited significant differences in trait values as well as the genetic architecture of the traits. Nevertheless, nonadditive genetic and maternal environmental effects tended to be larger than the additive genetic effects. There was also a shift from maternal environmental to genetic effects during development in two of the populations. That is, maternal environmental effects were larger at early (egg and alevin) life stages, whereas nonadditive effects were larger at the later (fry) life stage. The amount of additive genetic effects was small, suggesting the traits will respond slowly to selection. We discuss how different maternal environmental effects across years may influence the genetic architecture of offspring traits.
We used remote sensing chlorophyll a concentration data, spring copepod abundance, and individual fish condition information to understand the annual recruitment variability of two neighboring ...haddock (Melanogrammus aeglefinus) stocks in the Gulf of Maine region. When we considered the full range of recruitment variability, the abundance of the copepods Calanus finmarchicus and Pseudocalanus spp. failed to explain the variation in survivor ratio in either stock. However, when we examined this relationship with subsets of the data, we found that Pseudocalanus spp. appears to have had an effect on survivor ratio. The full range of recruitment variability of the Georges Bank stock was found to correlate with the timing and size of the fall bloom the year before recruitment, which has been termed the parental condition hypothesis, suggesting that the fall bloom affects the condition of spawning adults and thus recruitment. The absence of a correlation between fall bloom and recruitment in the Gulf of Maine stock can be attributed to the difference in fall bloom frequency between the two stock areas. It appears that both parental condition and larval survival affect haddock recruitment; however, the relative impact of these effects depends on the contrasting nature of ecosystem environmental drivers.
For effective management of species of conservation concern, knowledge of life history parameters is essential. Here, we present the results of one of the longest ongoing capture-mark-recapture ...studies of juvenile green turtles (
Chelonia mydas
) worldwide. From 1988 to 2013, 1,279 individual turtles were tagged in Fernando de Noronha, Brazil (3°51′S, 32°25′W). The size distribution at first capture varied between 27 and 87 cm (mean ± SD 47.9 ± 11.3 cm) curved carapace length (CCL). Median residence time was 2.4 year (with long-term residence of up to 11.2 year), with individuals exhibiting some site fidelity within the Archipelago. Turtles at this site are slow growing (mean 2.6 ± 1.6 cm year
−1
; range −0.9 to 7.9 cm year
−1
;
n
= 1,022), with a non-monotonic expected growth rate function and a peak in growth rates occurring at 50–60 cm CCL. At these rates, turtles in Fernando de Noronha would need to spend ca. 22 years to grow from 30 to 87 cm CCL and even longer to reach minimum adult breeding size. A Cormack–Jolly–Seber model was used to estimate the apparent survival of the residents and recapture probabilities (2001–2012). The estimated annual abundance ranged from 420 to 1,148 individuals. Confidence around abundance estimates was low, and there was no significant trend over the period, despite steep recent increases at the major source rookery. Slow growth and stable stocking numbers may be suggestive of density-dependent regulation having taken place following initial population recovery that occurred prior to the current study.
