Introduction to trophology of walleye pollock

Various aspects of walleye pollock feeding at different stages of its ontogenesis are reviewed and discussed. Structure and functional features of its mouth organs are considered with meristic and quantitative description of the filter one. Lists of pollock prey are presented with attention to changes of food composition and dominant species in the process of its growth from larvae to adult fish. Daily rhythm of feeding is not usual for pollock, but it appears locally and temporary under regional or seasonal conditions of its prey (i.e. plankton). An important feature of the pollock trophology is cannibalism on its own larvae and underyearlings that allows to the population to extend the food spectrum toward small-sized zooplankton. Activity of the pollock feeding can change in several times during the year in dependence on food resources and physiological state of the fish. Year-to-year variability of mass groups of prey (copepods, euphausiids, hyperiids) abundance sometimes coincides with the pollock stock changes in the northern Okhotsk Sea, but variations of arroworms abundance (not important for pollock) never coincide with the stock changes. Daily food ration of pollock (relative to body weight) decreases with its age, but its absolute individual consumption increases that could be a reason of food conversion underestimation. However, large fish are few and feed mostly on fish and benthic invertebrates (similar to cod), so their consumption of zooplankton could be ignored.

Experimental Rearing of Spiny Lobster, Panulirus homarus (Palinuridae) in Land-Based Tanks at Mirbat Station (Sultanate of Oman) in 2009-2010

Two experiments on the rearing of the spiny lobster Panulirus homarus were conducted in land-based tanks at Mirbat Aquaculture Unit from June to December 2009 and January-December 2010. In the first experiment 14 lobsters with an average size of 64.9±7.4 mm CL and weight of 297.8±98.0 g were reared to an average of 71.7±7.2 mm CL and weight of 384.0±114.8 g over 187 days. In the second experiment 45 lobsters were reared from an initial length of 45.4±4.6 mm CL and weight of 118.9 g to a length 66.0±7.1 mm CL and a weight of 304.1 g over 335 days. Total length increment was 45.8% and weight increment 155.1%. The daily food ration was 3.0-8.8%. The survival rate in the first experiment was 92.9%, in the second experiment it was also high (86.7%) during the first six months. In both experiments males grew faster than females. While the water temperature, pH, salinity and dissolved oxygen reflected the ambient condition of the Arabian Sea, these were not optimal levels for lobsters culture. The salinity was higher (37.5 ppt), while the water temperature was low (<20oC) during the summer monsoon. The study demonstrated the possibility of cultivating sub-adult lobsters in Oman from 40–45 mm CL and 100 g to maturity stage, obtaining the legal size of 70 mm CL and a weight of about 350 g over a year. It is recommended that the next experiment be conducted in floating sea cages from October to June.

Regulation of food intake by neuropeptide Y in goldfish

In mammals, neuropeptide Y (NPY) is a potent orexigenic factor. In the present study, third brain ventricle (intracerebroventricular) injection of goldfish NPY (gNPY) caused a dose-dependent increase in food intake in goldfish, and intracerebroventricular administration of NPY Y1-receptor antagonist BIBP-3226 decreased food intake; the actions of gNPY were blocked by simultaneous injection of BIBP-3226. Goldfish maintained on a daily scheduled feeding regimen display an increase in NPY mRNA levels in the telencephalon-preoptic area and hypothalamus shortly before feeding; however, a decrease occured in optic tectum-thalamus. In both fed and unfed fish, brain NPY mRNA levels decreased after scheduled feeding. Restriction in daily food ration intake for 1 wk or food deprivation for 72 h resulted in increased brain NPY mRNA levels. Results from these studies demonstrate that NPY is a physiological brain signal involved in feeding behavior in goldfish, mediating its effects, at least in part, through Y1-like receptors in the brain.

Evidence that Feeding Motivation Alone cannot Explain Oral Stereotypy in Sows

There has been much debate on the causes of stereotypy, but the motivational bases of these abnormal behaviours have yet to be fully understood. In the case of oral stereotypies in sows, there is evidence that the motivation to perform feeding behaviour may be involved. Restrictively-fed sows are highly food-motivated for large periods of the day. It has been shown that high-fed gilts perform stereotypies at a lower rate than low-fed gilts indicating that the level of feeding is important (Terlouw et al., 1991). Oral stereotypies in sows occur largely within a specific time after the daily food ration has been consumed. In sows housed in barren pens stereotypy is expressed as excessive drinking or chewing bars or chains, while sows housed on straw will nose and chew the bedding excessively in the same time period after feeding (Burbidge et al, 1993). The behaviour patterns are similar to those used in normal food-searching behaviour, but occur in the absence of reward. It has been suggested that oral stereotypy is the result of the appetitive phase of foraging entering a closed loop of repetition as the normal goal, attainment of more food, cannot be achieved (Hughes & Duncan, 1988). Two experiments were designed to examine the behavioural response to size and frequency of food rewards and they represent the first in a series of experiments which investigate the bases of stereotypies.