Influence of peat substrate on the distribution and behaviour patterns of sand shrimp, Crangon septemspinosa, under experimental conditions

Peat harvesting is a lucrative industry in New Brunswick, Canada, and is for the most part located along the coast. Current methods of mining peatlands are such that high levels of peat fibers are transported by runoff into fresh and marine waters. To understand better the influence of peat substrate on aquatic organisms living in peat‐impacted habitats, the sand shrimp (Crangon septemspinosa) was used as a bioindicator. A series of laboratory experiments was conducted in which shrimp were provided with a choice between sand and peat. Long‐term studies on starved shrimp confirmed that whereas foraging activities took place on both substrates, shrimp display an overall preference for sand (73% of all shrimp observed were on sand, n=60). When food was deposited on each of the substrates, shrimp generally opted to feed on sand (75% of all shrimp observed were on sand, n=60). After all food on sand was consumed, shrimp tended to move to peat. This was followed by a short period of foraging on both sand and peat with an eventual return to sand in most instances. The presence of food on both substrates did not influence their preference for sand. However, shrimp will move onto a peat substrate to forage if food is present only there. This observation suggests that, although there is a marked preference for sand, peat is not completely repellent to them. Finally, histological investigations of the shrimp digestive system revealed that peat was ingested with food particles and processed in the gastric mill. There was, however, no discernible discrimination between the two substances during ingestion. Finally, starved shrimp on peat substrate did not ingest peat fibers, suggesting that peat is not perceived as an alternative food source.     

Abundance and distribution of sturgeon feeding pits in a Washington estuary

Sturgeon diet and feeding habitats are notoriously difficult to document. We mapped the locations of feeding pits in Willapa Bay, Washington, to characterize estuarine habitats used by sub-adult and adult sturgeon for infaunal feeding. Monthly summer surveys of intertidal plots revealed that feeding pit density was highest in July and August, when sturgeon occupy Willapa Bay. The ephemeral nature of feeding pits and high daily densities (> 1000 pits/ha) indicated intensive sturgeon feeding over unvegetated littoral mud flats during high tide. Feeding pit density was lowest in subtidal areas, over sand (grain sizes primarily >63 μ), and at sites with dense stands of non-indigenous seagrass, Zostera japonica. Sub-adult and adult sturgeon apparently used these habitats significantly less than would be predicted based on their availability. Feeding pit formation was negatively correlated with Z. japonica shoot dry weight and positively correlated with the abundance of thalassinid shrimp burrows. Experimental removal of Z. japonica resulted in increased sturgeon feeding, but experimental removal of burrowing shrimp did not significantly affect feeding pit formation. Aquaculture activities that harden substrate and proliferation of invasive seagrass both appear to produce estuarine substrates that are unsuitable for benthic feeding by sturgeon.     

Prevalence of the bopyrid isopod Probopyrus pandalicola in the grass shrimp, Palaemonetes pugio, in four tidal creeks on the South Carolina-Georgia coast

The grass shrimp, Palaemonetes pugio, is an important food source for many invertebrate and fish species, including several of commercial importance. The bopyrid Probopyrus pandalicola prevents reproduction in P. pugio by sexual sterilization. The purpose of our research was to determine bopyrid prevalence in grass shrimp over the course of a year. Shrimp were collected from 2 estuarine systems in South Carolina and 2 estuarine systems in Georgia and examined for parasite presence, sex, and gravidity. Site-specific monthly prevalence ranged from 0 to 6.3%. Country Club Creek had the maximum mean +/- SE prevalence of 3.1 +/- 0.3%, and Harbour Town had the minimum of 1.3 +/- 0.3%. Maximum prevalence was concurrent with peak gravidity for Moon River; thus, at this site the negative effect of this parasite on reproductive output may be greater. Reduced egg production may affect grass shrimp abundance and ultimately the recruitment success of its predators.     

Persistence and stability of macroinvertebrate communities in streams of Denali National Park, Alaska: implications for biological monitoring

1. Macroinvertebrate communities were studied from 1994 to 2001/2002 (except 1997) in six streams in Denali National Park, interior Alaska. All six streams were potential reference streams with no known impairment. 2. Abundance of individual taxa varied markedly from year to year. Overall, abundance decreased over the study period, particularly with respect to mayflies. Stonefly taxa showed lower persistence and were sometimes absent from a stream in any particular year. 3. Mean community persistence for the six streams, as measured by Jaccard's similarity coefficients between years, varied from 0.48 in the year pair 1999–2000 to 0.78 in 1998–99. Tattler Creek (a small stable stream) supported the most persistent macroinvertebrate community and Highway Pass Creek (a small, unstable creek) the least. Mean community persistence showed a significant relationship with mean winter snowfall (November to March) for the six streams. 4. The highest community compositional stability was found in Tattler Creek and the lowest in Highway Pass Creek, but stability varied markedly over time for the six streams, peaking in 1994–95 and reaching a minimum in 2000–01. Compositional stability was significantly related to the Pfankuch Index of channel stability. 5. The composition metrics % Chironomidae, % dominant taxa, %EPT, % Ephemeroptera and % Plecoptera, employed as part of the Alaska Stream Condition Index, varied over almost their entire range in these pristine streams across the 9 years of the study. 6. This study demonstrates the wide range of natural variation that occurs in benthic macroinvertebrate communities in these pristine central Alaskan streams, potentially limiting the applicability of composition metrics for the biological monitoring of water quality in these systems.     

Study on optimization of moisture retention for golf green rootzone soil mixtures

Most golf course green have been constructed with pure sand or sand-based rootzone mixes. As we know, high sand content provides rapid drainage despite sand’s inefficiency in retaining moisture. However, drainage capability and water retention are both essential elements to the golf course green, and the addition of peat could increase the soil moisture retention, therefore, the research on the drainage capability and water retention of the sandy golf green has become more and more important these years. In this study, extreme vertex design was applied which is one of the mixture experiment designs widely used in mixture experiments, the study investigated the effects of the thirteen different rootzone soil mixtures using middle-coarse, fine sand, very fine sand plus silt and clay as well as peat as the materials under three kinds of golf green profile (1-layer profile, 2-layer profile, 3-layer profile) conditions on the water retention of green rootzone. Through the qualitative, quantitative and optimization analysis of water retention capability of the sandy golf green, evidence a basis for choice of green profiles and rootzone matrix could be provided. And the significantly correlative regression model was established between the moisture retention and components of rootzone soil mixture. In addition, the order of factor contribution ratio, effect of single and double factor and optimization of the model were analyzed in detail. The results were as follows: both green profile and soil mixture, which had interaction of each other, had significant effects on soil moisture retention. Additional attributes include high porosity and greater water holding capacity than sand, and the higher content of peat, fine sand plus silt and clay, the better water retention. The mixtures had much higher water content in 1-layer profile than that in the other two profiles. There was significantly higher water content in 2-layer profile for pure sand mixtures (A–E) and low peat mixture (F) than that in 3-layer profile, while there was no higher water content for other 7 high peat mixtures (G–M) (>5%) in 2-layer than that in 3-layer profiles. The significance of key factors in rootzone soil mixture on moisture retention were: very fine sand plus silt and clay > peat > middle-coarse > fine sand. According to the moisture retention 15–25% specification of USGA (United States Golf Association), the optimal soil mixture in 1-layer profile was: middle-coarse 71.4–73.5%; fine sand 17.8–21.5%; very fine sand plus silt and clay 6.8–8.4%; peat 0–1%. The optimal soil mixture in 2-layer profile was: middle-coarse 65.0–73.4%; fine sand 17.8–20.5%; very fine sand plus silt and clay 7.5–8.9%; peat 0.2–6.3%. The optimal soil mixture in 3-layer profile was: middle-coarse 62.3– 73.9%; fine sand 17.7–21.4%; very fine sand plus silt and clay 7.3–10.7%; peat 0–6.3%. These optimal recipes took through the limitation of previous research, which were practically important to golf green soil selection and profile design. Thus, both proportion and interaction should be considered when we choose the soil mixture.     

The Challenge of Peat Substitution in Organic Seedling Production: Optimization of Growing Media Formulation through Mixture Design and Response Surface Analysis

Peat replacement is an increasing demand in containerized and transplant production, due to the environmental constraints associated to peat use. However, despite the wide information concerning the use of alternative materials as substrates, it is very complex to establish the best materials and mixtures. This work evaluates the use of mixture design and surface response methodology in a peat substitution experiment using two alternative materials (green compost and palm fibre trunk waste) for transplant production of tomato (Lycopersicon esculentum Mill.); melon, (Cucumis melo L.); and lettuce (Lactuca sativa L.) in organic farming conditions. In general, the substrates showed suitable properties for their use in seedling production, showing the best plant response the mixture of 20% green compost, 39% palm fibre and 31% peat. The mixture design and applied response surface methodology has shown to be an useful approach to optimize substrate formulations in peat substitution experiments to standardize plant responses.     

Effects of Acid Mine Drainage on the Estuarine Food Web, Britannia Beach, Howe Sound, British Columbia, Canada

We investigated the effects of acid mine drainage (AMD) from Britannia Creek, BC, Canada, a stream contaminated by an abandoned copper mine, on the estuarine food web. Near the mouth of Britannia Creek, sediments and the water contained high concentrations of dissolved copper and the waters were highly acidic. Relative to a reference location, rockweed (Fucus gardneriSilva) cover was reduced, phytoplankton biomass was lower, chironomid larvae were less abundant, and fewer gammarid amphipods colonized basket traps. Laboratory toxicity tests confirmed that sediments and water from the lower reaches of Britannia Creek and its estuary were highly toxic to midge larvae (Chironomus tentansFabricius), the marine amphipod (Eohaustorius washingtonianusThorsteinson) and also impaired fertilization of sand dollars (Dendraster excentricusEschscholtz). Analyses of stomach contents of chum salmon fry (Oncorhynchus ketaWalbaum) indicated that they preferred to feed on chironomid larvae and gammarid amphipods at Britannia Creek estuary but these two taxa were less abundant at Britannia Creek estuary relative to the reference location. AMD from Britannia Mine disrupted the structure and function of the intertidal ecosystem resulting in loss of food production for fish including chum salmon fry and other species.     

Pink bollworm moth （Lepidoptera： Gelechiidae） catches in the Imperial Valley, California from 1989 to 2003

We examined the patterns of male pink bollworm （PBW）, Pectinophora gossypiella （Saunders）, moth catches in gossyplure-baited traps over a 15-year period from 1989 to 2003 in the Imperial Valley, California, USA. Monitoring was conducted during periods when different pink bollworm areawide control strategies were being used. Numbers of male pink bollworm moths caught in gossyplure-baited traps progressively decreased each year from 1990 to 1994 during short-season cotton production. High numbers of male moths caught in traps from 1995 to 1997 may have been related to moth migrations from the large cotton acreages grown in the Mexicali Valley bordering the Imperial Valley. Transgenic Bollgard （Bt） cotton was planted in 3% of the cotton area in 1996 and thereafter in 80%- 94% of the cotton area from 1997 to 2003. Pink bollworm moth trap catches were significantly lower from 1998 to 2003 than catches in 1995 to 1997, except for 1999. The trapping results suggested that Bt cotton had significant input on reduction of pink bollworm populations, confirming results of other investigators and providing additional documentation on the benefits of the Bt cotton culture.     

Restoration of cut‐over bogs by floating raft formation: An experimental feasibility study

Abstract. Stimulation of floating peat by the introduction of poorly humified peat from four cut‐over bogs in The Netherlands was studied in a one‐year outdoor experiment. The pH of the various peat substrates was increased by adding different amounts of lime: 0–2 to 4–8 g‐CaCO₃.kg^‐1 fresh peat. Both peat type and lime addition were found to affect the buoyancy of the peat substrates. Low nutrient concentrations in the peat, together with a high bulk density, proved to be unfavourable for creating floating peat. Three of the peat types proved to be too acidic (pH < 4.5) to produce sufficient methane (ca. 400–600 μmol.L^‐1), and buoyancy was only achieved if lime was mixed in with the peat. The smallest amount of lime added (2 g.kg^‐1 fresh peat) was sufficient to maintain buoyancy for at least one year. Lime addition did not stimulate nutrient mobilization by mineralization, although P, N and K concentrations in the peat water were relatively high. It is concluded that floating peat can be initiated by the introduction of poorly humified peat. If the peat substrates are too acidic, lime can be added to stimulate buoyancy of the peat. Results are discussed in relation to restoration prospects.     

Suppressiveness to Fusarium oxysporum f. sp. radicis lycopersici in re-used perlite and perlite–peat substrates in soilless tomatoes

This work reports the occurrence of suppressiveness to Fusarium oxysporum f. sp. radicis lycopersici (FORL) on recycled perlite and perlite–peat mix from closed and open soilless systems. Nine soilless systems were sampled from three different sites in Northern and Southern Italy and different parameters, including sampling site, growing period before sampling, electric conductivity of the nutrient solution, tomato cultivar, and irrigation system were considered. The effects on seed germination and FORL incidence on tomato seedlings were finally assessed with or without additional artificial inoculation of the pathogen and with or without autoclaving the samples prior to inoculation. Suppression of FORL was experimentally evaluated with a technique already adopted for rockwool. Results collected on perlite and perlite–peat confirmed the possibility to reduce FORL severity on recycled substrates. Only the composition of the substrate (perlite, perlite–peat mix) and the disinfestation did affect the incidence of FORL. Suppression of FORL was observed in not disinfected recycled perlite–peat substrates while a reduction of FORL incidence was also been recorded in disinfected and recycled perlite. Disease incidence decreased from an average ranging from 44.4% to 61.9% in new perlite to 2.5–36.3% in recycled one. Similarly disease incidence decreased from an average ranging from 35.9% to 75.2% in new perlite–peat mix to 0.4–26.4% in recycled perlite–peat mix. In conclusion the recorded data suggest the possibility to consider FORL suppression as a predictable phenomenon when recycled substrates (perlite, perlite–peat mix) are adopted.     

Occurrence of Sanguinicola occidentalis Van Cleave and Mueller, 1932 in Perca flavescens and Campeloma decisum from a Michigan creek

Sanguinicola occidentalis (Trematoda: Sanguinicolidae) infected 58 (48%) of 120 yellow perch collected in 1997 and 40 (50%) of 80 yellow perch collected in 1998 from Silver Creek in lower Michigan. The mean intensity and mean abundance of this blood fluke were higher in 1998 than in 1997. The fluke was found in the bulbous arteriosus of the perch heart, free in the petri dishes when the gill filaments were teased apart, and in the body cavity washings, and 1 individual was associated with an eye. Of the 269 S. occidentalis examined from perch, none had eggs. Most perch examined and infected were only 1+ yr in age. Spearman's correlation coefficients between S. occidentalis intensity and host length in 1997 and 1998 were not significant. An additional 25 yellow perch (0+ yr in age) collected in 1998 were not infected. Thirty-seven (33%) of 113 snails (Campeloma decisum) examined in July and August 1999 from Silver Creek were infected with S. occidentalis.     

Allopatric distribution of juvenile red-legged banana prawns (Penaeus indicus H. Milne Edwards, 1837) and juvenile white banana prawns (Penaeus merguiensis De Man, 1888), and inferred extensive migration, in the Joseph Bonaparte Gulf, northwest Australia

During October to December 1997, we trawled estuarine habitats in the Joseph Bonaparte Gulf (JBG) to determine the distribution of juvenile red-legged banana prawns, Penaeus indicus (H. Milne Edwards, 1837) and white banana prawns, Penaeus merguiensis (de Man, 1888). We made 229 beam-trawls at 185 sites, mostly over a 100-m path (3-min duration). A Global Positioning System (GPS) receiver was used to verify our location. During October to December 1998, we intensively resampled three of the rivers that were sampled in 1997 to confirm the gulf-wide distribution of P. indicus and P. merguiensis and to investigate the microhabitat use of P. indicus. We chose previously sampled and new sites in Forsyth Creek (eastern JBG), the Lyne River (Cambridge Gulf), and the Berkeley River (western JBG). We made 249 trawls at 21 sites, mostly over 100 m.Juvenile banana prawns were abundant in eastern JBG, Cambridge Gulf and western JBG. They were not abundant in southern JBG, although fewer trawls were made there, due to its inaccessibility. In eastern JBG and Cambridge Gulf, over 96% and 73% (respectively) of juvenile banana prawns were P. indicus and they were more abundant there than in the western JBG. Conversely, in the western JBG over 93% of the juvenile banana prawns were P. merguiensis and they were more abundant than in the eastern JBG and Cambridge Gulf. The Lyne River in the northwestern Cambridge Gulf seems to be the transition zone; both P. indicus and P. merguiensis are equally abundant.P. indicus are most abundant on the mangrove-lined muddy banks of waterways within mangrove forests, similar habitats to P. merguiensis. Within these habitats, they were most abundant in gutters and small creeks, rather than rivers and large creeks. Few P. indicus or P. merguiensis were caught in 100 m² trawls undertaken midriver (on the channel bottom and on emergent banks), although these habitats may be only 100 m from the mangrove-lined habitats. In all creek and river habitats, both species are most catchable at low tide (irrespective of daylight or darkness) when they move out of the mangrove forests and accumulate in the remnant water bodies.The offshore fishery for P. indicus is in northwestern JBG in waters 50-80 m deep, about 300 and 200 km, respectively, from where juveniles are abundant in their extensive inshore habitats in east JBG and in Cambridge Gulf, demonstrating a geographical separation of the juvenile and adult phases. Postlarval P. indicus, spawned offshore, must use tides and currents to travel south and east to reach nursery habitats. Emigrant subadults must migrate north and west, across relatively shallow inshore sand substrates (30-40 m deep) to reach their offshore habitats.     

Growth of ornamental plants in two composts prepared from agroindustrial wastes

Two composts prepared from agroindustrial wastes were assayed as substrates: C1 from brewing waste (yeast and malt) plus lemon tree prunings; and C2 from the solid fraction of olive mill wastewater plus olive leaves. Sixteen substrates were prepared by combining each compost with Sphagnum peat or a commercial substrate (CS) in different proportions. The nutrients (N and K) provided by the composts, which acted as slow-release fertilisers, influenced especially the development of calendula, although the physical and physico-chemical properties such as total pore space and electrical conductivity (EC) were also relevant. On the other hand, in the salt-sensitive calceolaria hybrid, EC and chloride concentration were the main factors influencing growth. Adequate substrates for the development of calendula can be prepared by mixing C1 at up to 75% with peat or at up to 50% with CS, and C2 at up to 50% with peat or CS. For calceolaria, the substrate should have a lower proportion of compost, C1 at up to 50% and C2 at up to 25%, both mixed with peat or CS. Therefore, composts of agroindustrial origin such as these can be used as an alternative to peat and CSs for growing ornamental plants. provided the mixture contains at least 25% peat or CS.     

Use of municipal solid waste compost (MSWC) as a growing medium in the nursery production of tomato plants

Five media prepared from old peat (OP), white peat (WP) and municipal solid waste compost (MSWC) were used to determine optimum growing media for tomatoes (Lycopersicum esculentum Mill. cv "Atletico"). The mixtures of substrates used were: OP (65%)+WP (30%)+perlite (5%), OP (65%)+MSWC (30%)+perlite (5%), WP (65%)+OP (30%)+perlite (5%), WP (65%)+MSWC (30%)+perlite (5%), MSWC (65%)+WP (30%)+perlite (5%). Various seedling indices were measured in order to assess the quality of the nursery-produced plant. Nursery-produced tomato seedlings grown in WP (65%)+MSWC (30%) displayed quality indices similar to those recorded for conventional mixtures of old and white peat sphagnum, due to a correct balance between the compost nutrient supply and the porosity and aeration provided by white peat.     

Regeneration of Three <Emphasis Type="Italic">Sphagnum</Emphasis> species

Sphagnum capillifolium var. tenellum, S. magellanicum, and S. recurvum var. brevifolium were regenerated from stem pieces grown in containers to assess their potential for use in peatland restoration projects. The effect of two water levels; peat, peat/sand or peat/clay substrates; and peat decomposition level on the species’ regeneration was evaluated. S. magellanicum attained the greatest cover on the peat or peat/sand mixture using decomposed peat when the growing surface was occasionally inundated. S. recurvum attained the greatest cover grown on the peat or peat/sand mixture using undecomposed peat when the water level was kept below the surface. S. capillifolium showed an affinity for the peat/clay mixture, and overall attained a greater total cover than the other species when grown under the lower water level on all substrate types, with total cover approximately three to five times that of the others. When developing management plans for restoration of mined peatlands, species-specific responses to water level, type and extent of mineral soil mixed with the peat surface, and peat decomposition level should be considered.     

A modified drop-net method for sampling mobile epifauna on marine shallow sandy bottoms

The seasonal variations in numbers and biomass of the mobile epifauna of a shallow, sandy bay in Gullmar Fjord (Sweden) was investigated during 1976–1977 using the drop-net technique. Juvenile plaice, Pleuronectes platessa L., sand goby, Pomatoschistus minutus (Pallas), and brown shrimp Crangon crangon L. are the dominant epifaunal species. A net enclosing an area of 100 m² was used, and the organisms captured were collected with a small trawl. Three stations with a water depth≤ 1 m were regularly sampled with a total number of 73 drops. Maximum abundance was for plaice in June (6 ind m^-2), for the shrimp in July-August (61 ind m^-2), and for sand goby in September (2 ind m^-2). Standing stocks (dry wt) were 0.2, 1.5 and 0.2 g m^-2 respectively. Production estimates were based on seasonal changes in size frequency and information on specific growth rates. The production rate was for plaice (0-group) 0.3 g m^-2 yr^-1, for the shrimp 1.5, and for sand goby 0.2 g m^-2 yr^-1. Reliable estimates of the absolute abundance can be derived from the mean catch per unit area only when the efficiency of the fishing gear is known. After 6 hauls with the trawl in the drop-net enclosure more than 85% of the shrimps were caught and after the fifteenth haul less than 1% were still left. The fishing efficiency of a push-net in relation to the drop-net was for the shrimp 50%, for plaice 35% and for sand goby 17%.     

Late Pleistocene and Holocene environments of the Southeastern United States from the stratigraphy and pollen content of a peat deposit on the Georgia Coastal Plain

A 5.4 m peat core from the Sandy Run Creek (SRC) valley in the upper Coastal Plain of Georgia shows that before 30 ka the valley had an aggradational sandy floor with shallow swales and low ridges of 1–2 m amplitude suggesting a braided stream pattern and a low water table. The climate from 30–25 ka was cool and dry and the vegetation open grassland with stands of pine and spruce that produced few fires. At ca. 16 ka a warmer, wetter climate caused SRC to meander and incise the valley fill removing some previously deposited sediment at the site of our peat core so that sediments of 13 ka rest directly on sediments deposited at 25 ka. After ca. 13 ka higher groundwater levels initiated vertical accretion of floodplains allowing peat accumulation in shallow depressions across the valley. Pollen from the Younger Dryas period (ca. 13–11 ka) indicates a cool, moist environment of open oak woodland, mesic trees, riparian populations of alder, and reduced levels of pine. By the early to mid Holocene, tupelo and oak dominated over pine indicating wetter conditions, while sand stringers in peat record periodic heavy rains, an elevated water table, and intervals of substantial runoff. Cooling after ca. 4.5 ka brought drier and more variable conditions. Fires increased and southern pine replaced tupelo and oak. The absence of sand stringers in peat younger than 4.5 ka indicates fewer intense rainfall events.     

Variation in penaeid shrimp growth rates along an estuarine salinity gradient: Implications for managing river diversions

Freshwater inflows from river diversions may affect nekton populations by altering the salinity and temperature of estuarine waters. To investigate the influence of these environmental variables on the growth and survival rates of brown shrimp Farfantepenaeus aztecus and white shrimp Litopenaeus setiferus, we conducted field experiments in May and September 2007 to expose experimental animals to the range of different combinations of salinity and water temperature that commonly occur in an estuarine environment. Growth rates for shrimp held in mesocosms for approximately 7 days were compared among four locations and three treatments; locations were identified by the dominant marsh vegetation and distance from the Gulf of Mexico (low to high salinity: Intermediate, Brackish, Saline UE = Saline Up Estuary, Saline DE = Saline Down Estuary). At each location, the treatments were replicated four times and included shallow water with additional food, shallow water without food added, and deeper water (an attempt to expose animals to lower temperatures). Our experiments were designed to test the null hypothesis that shrimp growth and survival rates did not differ by location or treatment. Both brown shrimp and white shrimp grew more slowly at the Intermediate than higher salinity locations. Potential prey (benthic infauna) biomass was relatively low at both the Intermediate and Brackish locations in May, and both shrimp species consistently grew faster in mesocosms where food was added. We conclude that reduced growth in low salinity environments is likely due to the combined effects of increased metabolic costs and less food in these areas. River diversions that reduce estuarine salinities over a large portion of available habitat during peak recruitment periods may reduce overall growth rates and shrimp productivity in the affected areas.     

Harvest Effects on Blood Pythons in North Sumatra

Wildlife populations exposed to intense harvesting often exhibit shifts in attributes of the commercial offtake (e.g., numbers, body sizes, body condition, sex ratios, size at maturation, reproductive frequency). To look for such changes, we examined >2,500 specimens of field-collected blood pythons (Python brongersmai) brought to 2 processing facilities in North Sumatra over 2 survey periods (1996–1997 and 2014–2015). Over the 18 years between our surveys, approximately 900,000 blood pythons were taken from Indonesia for the commercial trade; North Sumatra accounted for about 35% of that trade volume. Between survey periods, numbers of snakes brought to 1 processing facility decreased and mean body size increased, whereas at the second facility numbers and sizes of snakes remained the same. Overall, the pythons collected in 2015–2016 were thinner-bodied than in 1996–1997, with fewer immature animals and a reduced size at maturation and reproductive frequency among females. Clutch size relative to maternal size decreased also. These temporal shifts in python demographics likely reflect a response to harvesting, although ecosystem changes may have played a role. Compared to other squamate reptiles, blood pythons may be more vulnerable to over-harvesting because most snakes are intensively collected from discrete habitat patches (oil palm plantations), and the species can be targeted by specific hunting methods. To ensure sustainability of the harvest, we recommend minimum and maximum size limits for skins used in the commercial trade, and more intensive monitoring at processing facilities. © 2019 The Wildlife Society.     

The impact of mechanical harvesting regimes on the aquatic and shore vegetation in water courses of agricultural areas of the Netherlands

It was demonstrated that a mechanical harvesting regime can influence the species composition of ditch vegetation at the community level. This effect, however, was very small compared with those of other factors such as the between-site and the within-site spatial variation, and several soil and water quality parameters. Cutting in November had the largest effect, in that it caused the greatest extremes in species cover. The vegetation was composed of 136 plant species. The semi-aquatic and aquatic species were less numerous than the terrestrial ones (52 versus 84). The total number per vegetation type and site ranged from 5 to 49; that of persistent plant species, from 4 to 22. Only 16% of the species was significantly influenced by the mechanical harvesting regime. The significant effects of the mechanical harvesting regime on plant species were related to plant-inherent factors. Mechanical harvesting repeated within a year, on one hand, opened up the vegetation, 1) freeing sites for colonization of new species, 2) improving the light climate for seedlings which had already colonized; on the other hand, it exhausted (carbohydrate) reserves of solitary species. Mechanical harvesting once a year in November had a contrasting effect in that it caused suffocation of the shore vegetation in spring by the not yet decomposed plant material harvested in autumn. The highest species richness was attained for the aquatic vegetation: on sand by cutting three times per year (in May, July and September), and on peat by cutting once a year (in November); and for the shore vegetation: on sand once a year (in May) and two times per year (in May and July), and on peat once a year (in May or November).