The ecology of the Gussage, a lined winterbourne

The Gussage, a Dorset winterhourne (intermittent chalk stream), has been used to convey water from a compensation borehole to the River Allen to supplement its flow to meet demand for water. Sections of the Gussage have been lined with chalk, butyl sheeting or polythene sheeting to prevent water loss through the porous bed. The effects of this major environmental modification associated with these abstraction practices in the winterbourne catchments have been studied in the Gussage system since 1973. To compensate for the lack of adequate pre-lining data, comparative studies have been made on 3 small unlined chalk streams of varying flow regimes, ie. the Crichel (a winterbourne), the North Winterbourne and the Tarrant (permanent discharge in the reaches studies). The distribution of macrophytes and invertebrates in winterbournes are compared with that in natural and artificial permanent streams. Statistical analysis showed samples from the winterbourne sites and the unmodified permanent stream sites are quite distinct, despite the fact that no samples were taken from winterbourne sites during the dry phase. This emphasizes the differences between the fauna of an intermittent and a permanent stream and suggests that alteration of the flow regime could be a significant factor. Where flow regime has been altered, as in the Gussage downstream of the borehole, the samples occupy an intermediate position. Within this group of modified sites there is no apparent gross difference between the invertebrates of lined or unlined reaches.

The Chironomidae and their ecology in chalk streams

The taxonomy of the family Chironomidae is first discussed in this article, since there is considerable confusion over nomenclature. The author goes on to consider various aspects of the ecology of the family in chalk streams; preliminary studies on a reach of the Tadnoll Brook supplying most of the information.

Fungal and protozoan parasites and their importance in the ecology of the phytoplankton

The presence of fungi on the phytoplankton of Lake Windermere was first noted by the author in 1943. Surveys into the fungal and protozoan parasites of the planktonic algae of the English Lake District and elsewhere were carried out. This article discusses the descriptive studies, epidemics and culture work, which was carried out in connection with these studies.

Ceratium hirundinella - ecology of a complex, mobile, and successful plant

Recent work carried out in the English Lake District (Esthwaite Water and Blelham Tarn) is reported. The seasonal growth cycle, diel growth cycle, photosynthesis, vertical distribution and migrations, horizontal distribution, and the interaction of environmental factors, were investigated.

The ecology of chalk-stream invertebrates studied in a recirculating stream

To study and qualify the factors influencing interactions between various trophic levels in natural hard-water streams, a recirculating artificial stream channel was constructed. This structure has enabled patterns of population change of stream fauna to be observed under partially controlled physical and chemical conditions. Initial colonization of the substratum by invertebrates and subsequent succession was studied along with depth distribution and growth and production studies of invertebrates.

Physiological ecology of the ciliated protozoon Loxodes

Loxodes faces special problems in living close to the oxic-anoxic boundary. In tightly-stratified ponds like Priest Pot its optimum environment may be quite narrow and it can be displaced by the slightest turbulence. Loxodes cannot sense an O sub(2) gradient directly but its ability to perceive gravity allows it to make relatively long vertical migrations. It is also sensitive to light and oxygen and it uses these environmental cues to modulate the parameters of its random motility: in the dark, it aggregates at a low O sub(2) tension and in bright light it aggregates in anoxic water. The oxic-anoxic boundary is also a zone where O sub(2) may be a scarce and transient resource, but Loxodes) can switch to nitrate respiration and exploit the pool of nitrate that often exists close to the base of the oxycline.

Behavior ecology of the Humboldt squid, Dosidicus gigas: insights from an animal-borne video and data logging system

Dosidicus gigas is a large pelagic cephalopod of the eastern Pacific that has recently undergone an unexpected, significant range expansion up the coast of North America. The impact that such a range expansion is expected to have on local fisheries and marine ecosystems has motivated a thorough study of this top predator, a squid whose lifestyle has been quite mysterious until recently. Unfortunately, Dosidicus spends daylight hours at depths prohibitive to making observations without significant artificial interference. Observations of this squid‟s natural behaviors have thus far been considerably limited by the bright illumination and loud noises of remotely-operated-vehicles, or else the presence of humans from boats or with SCUBA. However, recent technological innovations have allowed for observations to take place in the absence of humans, or significant human intrusion, through the use of animal-borne devices such as National Geographic‟s CRITTERCAM. Utilizing the advanced video recording and data logging technology of this device, this study seeks to characterize unknown components of Dosidicus gigas behavior at depth. Data from two successful CRITTERCAM deployments reveal an assortment of new observations concerning Dosidicus lifestyle. Tri-axial accelerometers enable a confident description of Dosidicus orientation during ascents, descents, and depth maintenance behavior - previously not possible with simple depth tags. Video documentation of intraspecific interactions between Dosidicus permits the identification of ten chromatic components, a previously undescribed basal chromatic behavior, and multiple distinct body postures. And finally, based on visualizations of spermatophore release by D. gigas and repetitive behavior patterns between squid pairs, this thesis proposes the existence of a new mating behavior in Dosidicus. This study intends to provide the first glimpse into the natural behavior of Dosidicus, establishing the groundwork for a comprehensive ethogram to be supported with data from future CRITTERCAM deployments. Cataloguing these behaviors will be useful in accounting for Dosidicus‟ current range expansion in the northeast Pacific, as well as to inform public interest in the impacts this expansion will have on local fisheries and marine ecosystems.

Proceedings of the international workshop on the ecology and fisheries for tunas associated with floating objects

It has long been known that tunas frequently associate with floating objects, such as trees washed out to sea during periods of heavy rainfall, and fishermen have taken advantage of this behavior to facilitate the capture of fish. In some coastal areas, such as the Philippines, artisanal fishermen construct anchored fish-aggregating devices (FADs) to attract fish. More recently, large numbers of free-floating FADs have been constructed for deployment by large purse seiners on the high seas. The FADs often can be interrogated by the seiner and located at great distances using radio telemetry and/or GPS (Global Positioning System) technologies. In some cases a fleet of fishing vessels has a tender vessel which deploys and maintains the FADs, and notifies the fishing vessels when fish are seen around them. This workshop was convened by the Inter-American Tropical Tuna Commission and sponsored by Bumble Bee Seafoods, Inc., for the purpose of bringing together scientists and fishermen who have studied the association of tunas with floating objects. Special efforts were made to get participants from all the areas in which tunas associated with floating objects are the targets of fisheries. Thus the "regional review papers" include contributions for the eastern Atlantic, the southern Caribbean Sea, the Indian Ocean, and the eastern and western Pacific Oceans. Many of these reviews and other contributed papers are published in this proceedings volume. Other papers discussed in the workshop were published elsewhere; these papers are cited in the list of background documents in the Report of the Workshop.

Molecular ecology of european mustelids: Unraveling evolutionary and ecological patterns in Martes and Lutra genera

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The abiotic ecology of breeding ground of Palaemonid prawns in the Ilaje Estuary, Ondo State, Nigeria

In situ ecological assessment of the breeding grounds of palaemonid prawns was conducted in some selected locations around Ondo state coastal area between the months of April and September. Data obtained were subjected to both descriptive and inferential statistics. Three species of Palaemonid prawns were identified in four different locations within the study area with relative abundance ratio of 4:3:1. Macrobrachium macrobrachion, Nematopalaemon hastatus and Palaemon maculatus respectively. Sex ratio of 1 male to 5 females for M. macrobrachion, and 1 male to 2 females for N. hastatus and P. maculatus were observed with result showing significant relationships (P < 0.05) in distribution patterns across collection sites. Population distribution within the water column showed that palaemons are sub-lithoral prawns inhabiting maximum mean depth of 0.67m ± 0.025. Surface macro-phytes such as Eichhornia crassipies, Paspalum vaginatum, and Pistia stratiotes are common providing hiding spots for the prawn at the breeding ground. The mean soil pH across the sites stands at 6.67± 0.399 with the soil textural class that range from silty-loam to silty-clay. Also, the water quality parameters of study areas suggest that captive culture and rearing of Palaemons may be feasible outside the breeding areas.

The ecology and management of the European grayling Thymallus thymallus (Linnaeus). Interim report

The European grayling, Thymallus thymallus, is a highly under-rated freshwater fish, particularly in the United Kingdom. As such, little scientific research has been conducted on its biology, ecology or specific management plans, in comparison to the related species, salmon, Salmo salar L. and brown trout, Salm.o trutta trutta L. or the nearest relative to T. thymallus, the Arctic grayling, Thymallus arcticus (Walbaum), whose life history has been well documented in view of its high ranking by anglers, as a game fish. However, the importance of sound scientific research cannot be over stressed for this species, which can potentially provide an excellent fishery and source of income in salmonid depauparate rivers. The aim of this report therefore, is to review all available information on the biology, ecology and management of the European grayling, T. thymallus, incorporating findings for T. arcticus to bridge subjects where the literature is scarce, and propose management strategies for T. thymallus in the United Kingdom, bridge subjects where the literature is scarce, and propose management strategies for T. thymallus in the UK.

Aspects of the ecology of the crustacean zooplankton in the Sanyati Basin, Lake Kariba

Investigations on the zooplankton in Lake Kariba were carried out as part of a broader programme investigating components of the sardine, Limnothrissa miodon, food chain and factors affecting their productivity. This report deals mainly with the crustacean zooplankton, Bosmina longirostris and Mesocyclops leuckarti, which are the most important species in the sardine's diet. Factors which influence the number and distribution of the zooplankton are discussed. The relationship between the zooplankton and Limnothrissa are also briefly discussed.

Comparative feeding ecology of two elasmobranch species, Squalus blainville and Scyliorhinus canicula, off the coast of Portugal

The small-spotted catshark (Scyliorhinus canicula) (Linnaeus, 1758) and the longnose spurdog (Squalus blainville) (Risso, 1826) are two species occurring in the European and western African continental shelves with a wide geographical distribution. In this study, the diet of S. blainville and S. canicula off the Portuguese western Atlantic coast was investigated in 2006 by collecting monthly samples of these two species from local fishing vessels. In the stomachs of both species, crustaceans and teleosts were the dominant prey items, and molluscs, polychaetes, echinoderms, and sipunculids were found in lower abundance. In S. canicula, urochordate and chondrichthyan species were also observed in stomachs and were classified as accidental prey items. Scyliorhinus canicula consumed a broader group of prey items than did S. blainville. A significant diet overlap was observed, despite both species occupying different depth ranges over the continental shelf. Scyliorhinus canicula exhibited a consistency in diet composition among seasons, sexes, and maturity stages. Nonetheless, for both adults and juveniles, an increase in relative abundance of teleosts in the diet was observed in the spring and summer. This study provides evidence of the importance of S. canicula and S. blainville as benthic and pelagic predators along the western Atlantic coast.

Feeding ecology of juvenile Pacific salmon (Oncorhynchus spp.) in a northeast Pacific fjord: diet, availability of zooplankton, selectivity for prey, and potential competition for prey resources

We investigated the feeding ecology of juvenile salmon during the critical early life-history stage of transition from shallow to deep marine waters by sampling two stations (190 m and 60 m deep) in a northeast Pacific fjord (Dabob Bay, WA) between May 1985 and October 1987. Four species of Pacific salmon—Oncorhynchus keta (chum) , O. tshawytscha (Chinook), O. gorbuscha (pink), and O. kisutch (coho)—were examined for stomach contents. Diets of these fishes varied temporally, spatially, and between species, but were dominated by insects, euphausiids, and decapod larvae. Zooplankton assemblages and dry weights differed between stations, and less so between years. Salmon often demonstrated strongly positive or negative selection for specific prey types: copepods were far more abundant in the zooplankton than in the diet, whereas Insecta, Araneae, Cephalapoda, Teleostei, and Ctenophora were more abundant in the diet than in the plankton. Overall diet overlap was highest for Chinook and coho salmon (mean=77.9%)—species that seldom were found together. Chum and Chinook salmon were found together the most frequently, but diet overlap was lower (38.8%) and zooplankton biomass was not correlated with their gut fullness (%body weight). Thus, despite occasional occurrences of significant diet overlap between salmon species, our results indicate that interspecific competition among juvenile salmon does not occur in Dabob Bay.

Feeding ecology of Atlantic bluefin tuna (Thunnus thynnus) in North Carolina: diet, daily ration, and consumption of Atlantic menhaden (Brevoortia tyrannus)

Diet, gastric evacuation rates, daily ration, and population-level prey demand of bluefin tuna (Thunnus thynnus) were estimated in the continental shelf waters off North Carolina. Bluefin tuna stomachs were collected from commercial fishermen during the late fall and winter months of 2003–04, 2004–05, and 2005–06. Diel patterns in mean gut fullness values were used to estimate gastric evacuation rates. Daily ration determined from mean gut fullness values and gastric evacuation rates was used, along with bluefin tuna population size and residency times, to estimate population-level consumption by bluefin tuna on Atlantic menhaden (Brevoortia tyrannus). Bluefin tuna diet (n= 448) was dominated by Atlantic menhaden; other teleosts, portunid crabs, and squid were of mostly minor importance. The time required to empty the stomach after peak gut fullness was estimated to be ~20 hours. Daily ration estimates were approximately 2% of body weight per day. At current western Atlantic population levels, bluefin tuna predation on Atlantic menhaden is minimal compared to predation by other known predators and the numbers taken in commercial harvest. Bluefin tuna appear to occupy coastal waters in North Carolina during winter to prey upon Atlantic menhaden. Thus, changes in the Atlantic menhaden stock status or distribution would alter the winter foraging locations of bluefin