Use of state‐space modelling to identify ecological covariates associated with trends in pinniped demography

1. Identifying and understanding ecological drivers that influence wildlife populations is challenging but critical for conservation. This typically requires integrating long‐term data on both the population and potential drivers within statistical models that are suitable for analysing these complex relationships. State‐space models offer one method for integrating such data. Once implemented within a Bayesian framework, these analyses can control for multifactorial influences on populations, allowing one to extract otherwise undetectable correlations between the environment and the underlying, inferred demography.
2. In the Moray Firth, Scotland, harbour seals have been counted annually for 30 years (1988–2018). A Bayesian state‐space model was used to explore whether patterns in vital rates were correlated to changes in prey abundance, inter‐specific competition (grey seal abundance), environmental variables [the North Atlantic Oscillation (NAO) and sea‐surface temperature], or level of biotoxins (saxitoxin and domoic acid) in the Moray Firth waters.
3. The credible interval of the posterior distributions of three of these covariate coefficients (sandeel proxy, NAO and grey seal abundance) suggested that there was a relationship between those covariates and vital rates. Both the sandeel proxy and NAO showed a positive correlation with fecundity, whereas grey seal abundance had a negative impact on pup survival.
4. This work demonstrates how an integrated state‐space modelling approach can bring together diverse data sets and point to important interactions with prey, and with other predators in the system. This suggests that the wider‐scale management of UK harbour seal populations with their contrasting temporal trends needs to account for variation in the marine ecosystem at appropriate spatial scales, in line with current policy concerning spatial planning in the marine environment.

     

凤城地区保护性耕作应用经验探讨

为提高凤城地区玉米生产的可持续性,根据当地的农业基本情况,探讨在该地区实行保护性耕作技术的重要意义,总结该地区实施该技术的具体情况、采取的主要措施和取得的生态、社会、经济效益。     

丹东地区种植冬油菜可行性试验

通过对冬油菜品种的适应性、播种时间、种植密度等内容进行试验对比,确定陇油6号适于在丹东地区种植,其越冬成活率受环境因素影响较大;冬油菜越冬能力最强为叶龄8叶左右,适宜播种时间为8月末,种植密度为每5.0万~6.0万株/666.7 m~2。     

Evidence for long‐term spatial displacement of breeding and pupping harbour seals by shellfish aquaculture over three decades

• 1. Shellfish mariculture is increasing worldwide and often occurs adjacent to marine mammal breeding and feeding habitat. To better understand breeding pinniped vulnerability to potential shellfish mariculture disturbance and displacement effects in a US National Park, potential mechanisms were explored that may affect the proportion of harbour seals (Phoca vitulina) selecting high quality haul‐out sites near shellfish aquaculture within a large colony, and overall seal utilization of that colony in relation to other regional colonies.
• 2. Seal haul‐out sites isolated from the mainland (no predator access) had higher pup:adult ratios, indicating they are generally more important for pupping. Short‐term human disturbance did not have a significant effect on spatial use, but rather spatial use was pre‐determined by general sandbar isolation. Using multiple competing hypothesis and an information‐theoretic approach, it was found that within the estuary, after removing effects of El Niño, the proportion of seals (total seals and pups only) hauled out near mariculture sites was 8 ± 2% lower during years of higher oyster harvest. Annual oyster harvest was used as a measure of aquaculture activity that could result in direct disturbance or indirect displacement of harbour seals.
• 3. At the regional scale, oyster harvest, seal counts at a nearby colony, and loss of a major haul‐out site within the estuary, best explained pup and total seal use compared with the region. Regional population size, short‐term human disturbance rate, and other factors were not important. Concurrent with higher oyster harvest, the proportion of regional seals using the estuary declined by 7 ± 2% for seal pups (–65 ± 18 total pups), and 5 ± 2% for total counts ( ? 192 ± 58 total seals). These findings (both within the estuary and at the regional scale) were essentially identical whether modelling oyster harvest as either a continuous or categorical (low/high) variable and when using either frequentist or Bayesian statistical analyses.
• 4. Marine reserves set aside for wildlife may be less effective when the highest quality breeding and pupping sites are adjacent to regular aquaculture activities. These effects may not be detectable until additional natural variation lowers the quality of nearby habitats. Published in 2011. This article is a US Government work and is in the public domain in the USA.

     

Predation by seals on salmonids in two Scottish estuaries

Detailed observations of the behaviour of harbour seals, Phoca vitulina L., at sites within the estuaries of the Rivers Dee and Don, in north-eastern Scotland, were made over two full years between 1993 and 1996. Small numbers of grey seals, Halichoerus grypus Fab., were also present. The presence of seals within the estuaries was strongly related to season, with maximum numbers observed in winter and early spring; seals were virtually absent in June and July. The River Don was used largely as a haul-out site, while the River Dee was used predominantly as a foraging site, although it was not possible to determine whether the same seals were using the two estuaries. More seals were hauled-out on the River Don during twilight and dark than in daylight. The seals were observed to eat mostly salmonids, Salmo salar L. and S. trutta L., unidentified roundfish and flounder, Pleuronectes flesus L. The otoliths identified in scats collected at the mouth of the River Don belonged to marine species indicating that the seals were also feeding outside the estuaries. A minimum estimate is given of the numbers of large salmonids eaten in each river during the course of the year. Although no information was available on the numbers of salmonids using the rivers or the reproductive status of the fish eaten by the seals, as a cause of mortality, seal predation on large salmonids in estuaries is apparently an order of magnitude less important than mortality caused by angling within the river.     

论凤城市农业机械化发展

为加快凤城市的农业机械化发展速度,详细论述农业机械化在凤城市现代农业发展中的重要作用,根据凤城市农业机械化发展的实际情况,探讨其发展过程中存在的主要问题,并提出切实可行的应对措施。     

基于森林资源数据的凤城市森林不同龄组碳储量研究

为研究凤城市森林的碳储量,通过森林生物量—蓄积量回归模型,对森林资源变更数据按优势树种和不同林龄组的碳储量和碳储密度进行分析。结果表明:凤城市森林碳储量最大的树种是柞树,不同林龄碳储量由大到小依次为中龄林、幼龄林、成熟林、近熟林和过熟林;碳储密度由大到小依次为近熟林、中龄林、过熟林、成熟林和幼龄林。     

Managing contaminated sediments

While remediation and storage of contaminated dredged materials is a key issue at harbour sites, there is another type of sediment pollution problem, which mainly originates from large-scale dispersion of contaminants in flood-plains, dike foreshores and polder areas. In recent years, catastrophic cases of sediment contaminations have occurred in connection with the failure of tailing dams from mines. Unlike problems related to conventional polluted sites, the risks here are primarily connected with the transporting and depositing of contaminated solids in a catchment area, especially in downstream regions. A special example demonstrating the dispersion of highly contaminated sediments in a large catchment area will be shown from the so-called Chemistry Triangle of the upper Elbe River system, Germany. The Spittelwasser area, situated there, was chosen by the organisers of the international conference ConSoil 2000 for a case comparison and four expert teams from Denmark, Germany, the Netherlands and the UK were invited to participate in this Case Study. Evaluation of the plan was done by members of the networks of NICOLE (Network for Industrially Contaminated Land) and CLARINET (Contaminated Land Rehabilition Network). In the study of the German team, five major groups of technical measures have been identified by the environmental authorities to be discussed in relation to the Spittelwasser case or for similar problem solutions in contaminated flood-plain areas. The team came to the conclusion that none of these techniques would be applicable as an individual measure. Instead, a stepwise approach combining different monitoring techniques and remediation measures was proposed. These would include point excavations of critical material, promotion of plant growth as an element for stabilising the soil and flood sediments, as well as the installation of sediment traps. At the Spittelwasser site, investigations are planned on the effects of natural attenuation processes of organic and inorganic contaminants in flood-plain sediments and soils. In the practice of this concept, non-destructive, ‘intrinsic’ bonding mechanisms and their temporal development have thus far found much less recognition compared to destructive processes such as biological degradation. Yet these so-called ‘diagenetic’ effects, which apart from chemical processes involve an enhanced mechanical consolidation of soil and sediment components by compaction, loss of water, and mineral precipitations in the pore space, may induce a quite essential reduction of the reactivity of solid matrices [see Part I ‘Improving Chemical and Biological Criteria’ (JSS - Journal of Soils and Sediments, Vol 1, No 1, pp 30-36)]. Part IV ‘Subaqueous Storage/Capping of Dredged Material’ will be published in JSS No. 4 (December issue).     

Occurrence of killer whales in Scottish inshore waters: temporal and spatial patterns relative to the distribution of declining harbour seal populations

• 1. Sightings of killer whales around Shetland were recorded between 1991 and 2006 and for the whole of Scotland for 2007. The data were used to investigate temporal patterns in killer whale occurrence around Shetland and spatial patterns in occurrence around Scotland.
• 2. There was a strong seasonal peak in sightings around Shetland during June–July, coinciding with the harbour seal pupping season.
• 3. There was no clear trend in annual sightings around Shetland between 1991 and 2006.
• 4. Killer whales were sighted most frequently around Shetland and the Pentland Firth as well as around Mull and the Treshnish Isles.
• 5. These findings are discussed in terms of potential impacts upon local declining harbour seal populations and future research requirements.

Copyright © 2009 John Wiley & Sons, Ltd.     

Modelling the impacts of removing seal predation from Atlantic salmon, Salmo salar, rivers in Scotland: a tool for targeting conflict resolution

Abstract  Bioenergetics were used to model the potential impacts on adult Atlantic salmon, Salmo salar L., stocks and rod fisheries of removing harbour seals, Phoca vitulina L., from three rivers of different scales in the Moray Firth, Scotland, viz: the Spey (large), Conon (medium) and Moriston (small). Overall, seals had the greatest impact on the Moriston, where removal of a single animal could increase cumulative catch by 17% during the fishing season. On the Conon and Spey the impacts were negligible, and resulted in increased catches of <1% annually. On all rivers eliminating seal predation had the greatest impact during the spring due to the smaller size of spring salmon sub-stocks. A generalised model of seal removal illustrated that stocks and catches increased by >33% in rivers with monthly rod catches ≤10 fish, but declined to <10% for rivers with catches >34 fish. The outputs of the models are qualitative, but provide a management tool for targeting action to resolve seal-salmon fishery conflict. Smaller salmon population units, and spring salmon sub-stocks and fisheries in particular, are most vulnerable to predation. The merit of this approach is discussed regarding the management of Special Areas of Conservation for salmon and seals.