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Parameterisation of a population model for Acartia spp. in the southern Baltic Sea. Part 2. Egg production

Dzierzbicka-Głowacka L., Lemieszek A., Żmijewska M.I.

Oceanologia

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2009

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No. 51 (2)

185-201

EN

The paper describes the modelling of egg production in Acartia spp. under changing environmental conditions in the southern Baltic Sea (Gdańsk Deep). The hypothesis (Sekiguchi et al. 1980) that the food-saturated rate of egg matter production is equivalent to specific growth rate of copepods is applied. The average number of eggs produced per day by one Acartia female is obtained as a function of growth rate, i.e. by multiplying exp gN3-1 from the growth rate of the nauplius stage equation by Wfemale / Wegg. The copepod model, reduced to a zero-dimensional population model calibrated for Acartia spp. under the environmental conditions typical of the southern Baltic Sea, was used to determine the effects of temperature and food concentration on the growth rate of each of the model stages (see Part 1 - Dzierzbicka-Głowacka et al. 2009 - this issue). In this part, egg production as a function of the above parameters is evaluated. The rate of reproduction during the seasons in the upper layer of the Gdańsk Deep is also determined.

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Zmiany w produkcji jaj spożywczych w Polsce po przystąpieniu do UE

Sobczak J.

Problemy Inżynierii Rolniczej

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2007

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R. 15, nr 4

117-122

PL

Standardy unijne wprowadzając zmiany w systemach utrzymania kur nieśnych spowodowały konieczność wymiany wyposażenia technologicznego w blisko 80% kurnikach towarowych w Polsce. Ograniczenie obsady m2 powierzchni użytkowej o min. 30% w konsekwencji obniży liczbę jaj konsumpcyjnych pozyskiwanych przez producentów. Niepewność spowodowana nowymi przepisami może doprowadzić do wzrostu importu tanich jaj z innych państw, co przyczyniłoby się do obniżenia cen jaj wyprodukowanych w Polsce. Szansą polskiego drobiarstwa może być produkcja tzw. jaj "organicznych" lub "eko-jaj" pozyskiwanych w warunkach chowu z udziałem wybiegów lub specjalnych dodatków paszowych. Jaja takie uzyskują wysoką cenę na rynkach unijnych i są przyszłością na stołach bogatych konsumentów także w Polsce.

EN

European standards introduced definite changes in the keeping systems of laying hens, making necessary to replace the technological equipment in almost 80% laying hen houses in Poland. Limitation of the fowl density per m2 of useful surface by about 1/3 will consequently reduce the number of consumer eggs obtained by the producers. The uncertainty connected with new regulations may result in an increasing import of inexpensive eggs from the other countries. This would affect the price decline for eggs produced in Poland. The chance for Polish poultry farming may consists in production of so called "organic" eggs or "eco-eggs" obtained in layer keeping systems on the fowl yards or with special feed additives. Such eggs get a high price on the EU markets and are of the future on tables of wealthy consumers, also in Poland.

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Equivalence of rates of growth and egg production of Pseudocalanus

Dzierzbicka-Głowacka L.

Oceanological and Hydrobiological Studies

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2005

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Vol. 34, No.4

19--32

EN

The equivalence of rates of growth and egg production is analyzed for well-fed females of Pseudocalanus from Puget Sound (Washington, USA) and from the southern North Sea. The hypothesis is tested using published data on the Pseudocalanus species. The growth rates of the copepodite stages for species from these two regions as a function of temperature and food concentration were used. Quantitative expressions describing the effects of temperature and the cephalothorax length of females on potential reproductive rate were compared. Food-saturated egg production was computed as the mean number of eggs per sac divided by 1.25 times the embryonic duration at the given temperature. The calculations were done based on experimental data from the literature for some geographically separate populations of Pseudocalanus from southwest Baffin Island, Nova Scotia, Long Island Sound, Scotland, and the southern North Sea and adjacent waters. These values were compared with the average number of eggs produced per day by one female obtained here as a function of growth rate, i.e., multiplying exp gmax – 1 from the growth rate equation by Wfemale/Wegg. The combined effect of food concentration and temperature as a function of these two parameters on egg production (reduced by food limitation) was also established for Pseudocalanus from Puget Sound. These assumptions and estimations appear to predict the temperature-length of female dependent daily rates of egg production of well-fed females of Pseudocalanus spp. for the above waters. Suggestions are made as to how to obtain and present data to test this hypothesis more thoroughly.

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Potential rate of reproduction for some geographically separate populations of Pseudocalanus spp.

Dzierzbicka-Głowacka L., Zieliński A.

Oceanologia

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2004

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No. 46 (1)

65-83

EN

Quantitative expressions are presented describing the potential reproductive rate per individual female of Pseudocalanus spp. in several different waters (not reduced by food limitation) as a function of both temperature and cephalothorax length of females (one equation for each studied region). The calculations were made for some geographically separate populations of Pseudocalanus spp. from southwest Baffin Island, Nova Scotia, Long Island Sound, Scotland, as well as the southern North Sea and its adjacent waters (e.g. the English Channel). On the basis of the findings presented in this work and from other studies, the reproductive rate was computed as the mean number of eggs per sac divided by 1.25 times the embryonic duration at the given temperature. Also computed was the amount of egg matter produced per day as a percentage of body carbon (and dry weight) of female weight for all localities. The relationships for females from the southern North Sea were obtained for "viable eggs", but they should be treated with reserve. A more suitable expression describing egg production in the southern North Sea is the equation for females from the English Channel obtained here. Our assumptions and approximations appear to predict quite well the temperature-length of female dependent daily rates of egg production of well-fed females of Pseudocalanus spp. for the above waters, and we suggest that they can be used to test the hypothesis more thoroughly.