Effect of size on spawning time in the lesser sandeel Ammodytes marinus.

Ovarian development was examined in relation to size and temperature in late pre-spawning Ammodytes marinus over 5 years. Oocyte diameter was positively related to length indicating that larger females spawned earlier. Age and temperature, whilst accounting for the effect of length, were not found to affect oocyte development, although the thermal range examined was only 1·3° C.

Physiological and behavioral responses of poultry exposed to gas-filled high expansion foam.

Disease control measures require poultry to be killed on farms to minimize the risk of disease being transmitted to other poultry and, in some cases, to protect public health. We assessed the welfare implications for poultry of the use of high-expansion gas-filled foam as a potentially humane, emergency killing method. In laboratory trials, broiler chickens, adult laying hens, ducks, and turkeys were exposed to air-, N2-, or CO2-filled high expansion foam (expansion ratio 300:1) under standardized conditions. Birds were equipped with sensors to measure cardiac and brain activity, and measurements of oxygen concentration in the foam were carried out. Initial behavioral responses to foam were not pronounced but included headshakes and brief bouts of wing flapping. Both N2- and CO2-filled foam rapidly induced ataxia/loss of posture and vigorous wing flapping in all species, characteristic of anoxic death. Immersion in air-filled, high expansion foam had little effect on physiology or behavior. Physiological responses to both N2- and CO2-filled foam were characterized by a pronounced bradyarrythymia and a series of consistent changes in the appearance of the electroencephalogram. These were used to determine an unequivocal time to loss of consciousness in relation to submersion. Mean time to loss of consciousness was 30 s in hens and 18 s in broilers exposed to N2-filled foam, and 16 s in broilers, 1 s in ducks, and 15 s in turkeys exposed to CO2-filled foam. Euthanasia achieved with anoxic foam was particularly rapid, which is explained by the very low oxygen concentrations (below 1%) inside the foam. Physiological observations and postmortem examination showed that the mode of action of high expansion, gas-filled foam is anoxia, not occlusion of the airway. These trials provide proof-of-principle that submersion in gas-filled, high expansion foam provides a rapid and highly effective method of euthanasia, which may have potential to provide humane emergency killing or routine depopulation.

Sedimentation patterns caused by scallop dredging in a physically dynamic environment.

Scallop dredging grounds in the Firth of Lorn, western Scotland, are juxtaposed with rocky reef habitats raising concerns that reef communities may be impacted by sediment disturbed by nearby scallop dredging. A particle-tracking model of sediment transport and settling is applied at two scales. In the near-field, a suspension of typical sand/gravel-dominated bed sediment is subjected to a steady current across the dredge track. In the far-field, silt particles, which may persist in suspension for multiple tidal cycles, are tracked in the context of a regional model of tidally-driven flow. The principal sedimentary risk to reef habitats is predicted to come from settling sand particles when dredge tracks approach within tens of metres of a reef. The cumulative effect of dredging at the relatively low intensities recorded in this region is not expected to have a significant long-term impact on suspended silt concentrations and settlement in this highly dispersive environment.

Physiological responses of laying hens during whole-house killing with carbon dioxide.

1. Poultry on farms are sometimes required to be killed in an emergency, such as during a disease epidemic, yet none of the available methods are ideal. Whole-house carbon dioxide (CO(2)) administration has practical advantages, but gives rise to welfare concerns. 2. The study measured the body temperature, respiration, cardiac and brain activity (EEG) responses of 10 adult hens placed in tiered cages in a deep pit house while the entire flock (28,000 end-of-lay hens) was killed with CO(2). Video and thermographic images were also recorded. Liquid CO(2) was injected into the building producing a gaseous concentration of 45% within 19 min. 3. Those hens nearest the gas delivery site showed delayed respiratory, cardiac and EEG responses compared with those at more distant locations. Although sub-zero temperatures were recorded in the immediate vicinity of some birds, body temperatures indicated that they did not die of hypothermia. 4. EEG characteristics strongly associated with unconsciousness were used to determine an unequivocal time to loss of consciousness; this ranged from 6·0 to 10·5 (average 7·8) min after onset of gas injection. Distinctive cardiac and respiratory responses were seen following gas exposure; in particular, birds responded to inhalation of CO(2) by deep breathing. 5. The primary welfare concern is the duration of unpleasant respiratory effects, such as deep breathing, while the birds were substantively conscious. However, the concentration of CO(2) to which the birds were exposed while conscious would not have stimulated nasal and oral nociceptors. Time to death varied between 12·0 and 22·1 min after gas delivery.

Pain perception, aversion and fear in fish.

There is now compelling evidence that teleost fish possess similar nociceptive processing systems to those found in terrestrial vertebrates. Noxious stimulation of these nociceptors--specialised pain receptors -in the skin around the snout of fish generates neural activity that can be electrophysiologically recorded, and induces a number of behavioural and physiological changes. To determine whether changes in behaviour are more than simple responses to the noxious stimulation it is necessary to demonstrate that higher order cognitive processes such as mental state or 'affective state' are involved. However, quantifying the 'motivational affected state' of an animal--a concept encompassing not just pain but also fear, hunger, thirst and pleasure - is difficult owing to its subjectivity. Recent empirical work is beginning to test these concepts in fish, and we review a number of these studies and suggest how these general methodologies could be used to further our understanding of fish cognition and the capacity for fish to experience mental states such as fear or suffering.

The role of ultraviolet wavelengths in the mate-choice decisions of female three-spined sticklebacks.

Female three-spined sticklebacks have been found to use visual cues when responding sexually towards courting males, often preferring more intensely red-coloured males, and males with blue rather than silver irises. However, traditionally the literature has failed to test preference across the full spectral range to which females might be sensitive, limiting analysis to the human-visible wavelengths of the electromagnetic spectrum. We studied the effects that the addition of ultraviolet wavelengths has on the mate-choice preferences of female sticklebacks using a two-choice paradigm. We found that females preferred males that were viewed across the full spectrum to males whose display lacked an ultraviolet component. Using suitable controls we were able to establish that female preference was sexually motivated and was not caused by a general preference for the manipulated light conditions. Our results indicate that female preference may be due to an enhancement in visual contrast when males are viewed in full spectrum conditions.