Does motor noise from recreational boats alter parental care behaviour of a nesting freshwater fish?

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Evaluation of 10-year temporal and spatial variability in structure and growth across contrasting commercial thinning treatments in spruce-fir forests of northern Maine,USA

Key message

Detailed measures of growth pattern and structural heterogeneity applied in this study helped to quantify the immediate effects of various thinning regimes on forest structure and the resulting alterations in tree size as well as observed longer term stand dynamics.

Context

Forest management, stand structure, and tree growth are highly inter-correlated. Prior analyses, however, have resulted in mixed outcomes with limited success in revealing ecological mechanisms.

Aims

The study aimed at evaluating the relationship between forest structure and stand dynamics by applying several sophisticated measures of growth pattern and structural heterogeneity.

Methods

Data from a controlled and fully stem-mapped commercial thinning experiment with seven contrasting treatments including a non-thinned control at six locations across the Acadian Forest of Maine, USA, was used. Stand-level attributes examined included tree size and growth heterogeneity, spatial tree distribution, and growth dominance.

Results

Thinning generally reduced stand structural heterogeneity compared to the non-thinned control. In addition, the spatial arrangement of trees changed from fully random (non-thinned control) to a more clustered (removal of dominant and co-dominant individuals) or regular distribution (removal of intermediate and suppressed individuals). Overall, stand growth exhibited increasing (non-thinned control, removal of intermediate and suppressed individuals) or decreasing growth dominance of large trees (removal of co-dominant competitors). Forwarder trails increased basal area growth of individual trees up to a distance from the trail of approximately 5 m.

Conclusion

Findings of this study validate an earlier insight according to which interactions between management practices, forest structure, and tree growth form a permanent feedback loop.

     

Has agriculture dispersed worldwide from a single origin?

Some eleven thousand years ago hunter–gatherers in the Near East initiated their transition to farming using an assemblage of eight founder crops: three cereals, four legumes and flax. The evidence show that each of these plant species was brought into domestication once or mostly twice, with no further redomestication. It seems that these species were carefully chosen by humans from the many hundreds of plants used. Apparently, these eight crops were those that best responded to the sowing–reaping agrotechnique, reflecting the biological factors that were later manifested in the success of these founder crops. While changing their own life style, the novel, successful farmers have gained extra food, prestige, property, power, and as a result more spouses and children, eventually leading to their higher biological fitness. This in turn led to the expansion of agriculture either by idea diffusion or by the dispersal of the farmers themselves with their original founder crops. Farming has dispersed to Europe, Asia and North Africa during the following millennia. Concurrently, other remote hunter–gatherer populations in additional worldwide centers, notably East Asia and the Americas have also moved to farming life, conceiving local plant species and the relevant agrotechniques. Regarding the life history of the various cultivated plant species and the capabilities of our ancestors it is suggested that the simplest explanation for the beginning of agriculture in the new worldwide centers is the idea diffusion to these remote areas.     

Migrations and movements of Atlantic tarpon revealed by two decades of satellite tagging

Understanding large‐scale migratory behaviours, local movement patterns and population connectivity are critical to determining the natural processes and anthropogenic stressors that influence population dynamics and for developing effective conservation plans. Atlantic tarpon occur over a broad geographic range in the Atlantic Ocean where they support valuable subsistence, commercial and recreational fisheries. From 2001 through 2018, we deployed 292 satellite telemetry tags on Atlantic tarpon in coastal waters off three continents to document: (a) seasonal migrations and regional population connectivity; (b) freshwater and estuarine habitat utilization; (c) spawning locations; and (d) shark predation across the south‐eastern United States, Gulf of Mexico and northern Caribbean Sea. These results showed that some mature tarpon make long seasonal migrations over thousands of kilometres crossing state and national jurisdictional borders. Others showed more local movements and habitat use. The tag data also revealed potential spawning locations consistent with those inferred in other studies from observations of early life stage tarpon leptocephalus larvae. Our analyses indicated that shark predation mortality on released tarpon is higher than previously estimated, especially at ocean passes, river mouths and inlets to bays. To date, there has been no formal stock assessment of Atlantic tarpon, and regional fishery management plans do not exist. Our findings will provide critical input to these important efforts and assist the multinational community in the development of a stock‐wide management information system to support informed decision‐making for sustaining Atlantic tarpon fisheries.     

psbA Mutation (valine219 to isoleucine) in Poa annua resistant to metribuzin and diuron

The herbicide‐binding region of the chloroplast psbA gene from a total of 20 biotypes of Poa annua L resistant and susceptible to metribuzin and diuron was selectively amplified using PCR. Sequence analysis of the fragment from six herbicide‐resistant biotypes of P annua exhibited a substitution from valine to isoleucine at position 219 of the D1 protein encoded by the psbA gene. This is the same mutation as reported for Chlamydomonas and Synechococcus through site‐directed mutagenesis and in cell cultures of Chenopodium rubrum L. To our knowledge this is the first report of a higher plant exhibiting resistance in the field to photosystem II inhibitors due to a psbA mutation other than at position 264. The existence of additional biotypes of P annua resistant to diuron or metribuzin but lacking mutation in the herbicide‐binding region indicates that resistance to these herbicides can also be attained by other mechanisms. © 2000 Society of Chemical Industry     

Technical Note: The comparison of pH and redox potential in different locations in the reticulo-rumen of growing beef steers supplemented with different levels of quebracho extract

Rumen acidosis is a common metabolic disorder occurring when organic acid production exceeds clearance capacity, reducing ruminal pH. The occurrence of acidosis has been directly correlated to the ratio of concentrate to forage in the diet. However, rates of substrate fermentation and acid absorption vary at different locations in the reticulo-rumen. The objective of this study was to determine the pH and redox potential (Eh) in different locations of the reticulo-rumen using 16 ruminally cannulated steers (309 ± 43 kg) receiving different supplementation levels of quebracho extract (QT; Schinopsis balansae) within a grower type diet (CP: 13.4%; total digestible nutrients [TDN]: 70.4%; and ME: 2.55 Mcal/kg, dry matter [DM] basis). Animals were randomly assigned to one of four dietary treatments: QT at 0%, 1%, 2%, and 3% of DM (QT0, QT1, QT2, and QT3, respectively), containing about 0%, 0.7%, 1.4%, and 2.1% of condensed tannins (CT), DM basis, respectively. Animals were adapted to the basal diet for 12 d before being introduced to predetermined treatments for 4 weeks (wk), with diets provided twice daily to allow ad libitum intake. Weekly measurements of ruminal fluid pH and Eh were taken 4 h post-feeding using a portable pH meter with two probes (pH and redox) in four locations of the reticulo-rumen (reticulum, cranial sac, dorsal sac, and ventral sac). Data were analyzed using a random coefficients model with the pen as a random effect and wk as repeated measures, with DM intake included as a covariate. There was no interaction among treatments, location, and wk (P ≥ 0.882) on reticulo-ruminal pH. Overall, ruminal pH was lower for QT0 and QT1 compared to QT3 (P < 0.001). The pH in the reticulum was greater than those of the ventral and dorsal sacs (6.05 vs. 5.94, 5.89, respectively; P ≤ 0.001) but similar to cranial sac (6.00). Reticular pH was positively correlated with the ruminal locations (≥0.78; P < 0.001). The linear equation to estimate ruminal mean pH using reticulum pH had an intercept and slope different from zero (P ≤ 0.04), but CT (% DM) was not different from zero (P = 0.15), root mean square error of 0.15, and R² of 0.778: 0.723 (±0.36) + 0.857 (±0.059) × reticulum pH + 0.033 (±0.023) × CT. The Eh was lower for QT0 in week 1 than all other treatments (P < 0.001). We concluded that reticulo-ruminal pH differs among locations in the rumen regardless of QT supplementation level and days on feed, with reticular pH being the highest.     

Strategies for the capture and transport of bonefish, Albula vulpes, from tidal creeks to a marine research laboratory for long-term holding

Throughout their circumtropical distribution, bonefish ( Albula spp.) play a vital role in local economies as a highly prized sport fish. Recent interest in stock enhancement to sustain bonefish fisheries has led to the recognition that there currently are no data on how to live capture large numbers of adults (potential broodstock), transport them to captive facilities and how to handle them to ensure high survival. The objective of this study was to develop strategies for the capture and relocation of wild bonefish to a marine research holding facility to enable basic research and explore the potential for culturing bonefish for stock enhancement. Bonefish Albula vulpes (Linnaeus, 1758) were captured as they entered or left tidal creeks on Eleuthera, The Bahamas using seine nets and then transported by boat or truck to the laboratory. The relocation process evoked secondary stress responses at the metabolic, osmoregulatory and haematological levels as indicated by changes in blood glucose, lactate, haematocrit and ion values, relative to control fish. Physical and behavioural disturbances were also observed in bonefish that were unable to acclimate to laboratory conditions. Successful laboratory acclimation and long-term holding of wild bonefish was achieved through an adaptive learning process, whereby we identified a series of strategies and handling techniques to facilitate the acclimation of wild adult bonefish to captivity. This knowledge will enable future laboratory research on bonefish and is a prerequisite to the culture of this highly prized sport fish, and other sub-tropical and tropical marine species.     

A feasibility study for the application of climate change vulnerability assessments on species in the Tallurutiup Imanga National Marine Conservation Area

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Balanced nutrient density for broiler chickens using a range of digestible lysine-to-metabolizable energy ratios and nutrient density:Growth performance,nutrient utilisation and apparent metabolizable energy

Currently, specific nutrient concentration, metabolizable energy (ME) and digestible amino acids are used as feed formulation criteria. A balanced nutrient density (BND) concept based on 2 criteria of nutrient density and balanced amino acids-to-ME ratio may offer more flexibility in optimisation of profit in formulation of diets compared with current formulation based on set values per unit of feed mass. A total of 672 one-d-old off-sex male Ross 308 broiler chickens were used across two 42-d performance trials in a 3 × 2 factorial arrangement of treatments with each diet replicated 8 times (14 birds per replicate). The experimental factors were 2 nutrient density levels (low [LD] and high [HD]) and 3 digestible lysine-to-ME ratios (DLYS:ME; low, medium, and high). Low density diets had ME of 2,876 and 3,023 kcal/kg for starter and finisher, respectively, while values for HD diets were 3,169 and 3,315 kcal/kg with proportionally higher non-nitrogenated nutrients. Separate digestibility and apparent metabolizable energy (AME) assays were conducted at d 21 and 42. Digestibility assays at d 7 were conducted on birds used for performance trials. Regardless of the diet density, birds fed low DLYS:ME had a lower (P < 0.01) feed intake (d 0 to 42) than medium and high DLYS:ME. Without interaction, birds fed low and medium DLYS:ME had a similar body weight gain being the heaviest while birds low DLYS:ME were the lightest. By an interaction (P < 0.05), the highest overall FCR value was observed for birds fed LD × low DLYS:ME and improved linearly when DLYS:ME increased to the highest level reaching a limit for birds fed HD × medium DLYS:ME. Calorie conversion linearly decreased (P < 0.001) with increments in DLYS:ME. Jejunal and ileal starch and protein digestibility were affected on d 21 and 42 but not on d 7 of age. Given the independence of response on BW and feed consumption, the use of BND as a flexible system in diet formulations has the potential to enable more accurate formulation for optimisation of growth performance of broiler chickens.