Средняя индивидуальная масса особи (размеры животных) макрофауны пелагиали северо-западной Пацифики

• Main Author: Волвенко, Игорь
• Format: Text
• Language: unknown
• Published: Федеральное государственное унитарное предприятие «Тихоокеанский научно-исследовательский рыбохозяйственный центр» 2009
• Subjects: СЕВЕРО-ЗАПАДНАЯ ПАЦИФИКА; МАКРОФАУНА ПЕЛАГИАЛИ; СРЕДНЯЯ ИНДИВИДУАЛЬНАЯ МАССА ОСОБИ; РАЗМЕРЫ ЖИВОТНЫХ; Bering Sea; Okhotsk; Pacific; Rummage; okhotsk sea
• Online Access: http://cyberleninka.ru/article/n/srednyaya-individualnaya-massa-osobi-razmery-zhivotnyh-makrofauny-pelagiali-severo-zapadnoy-patsifiki; http://cyberleninka.ru/article_covers/3164276.png

По данным 19436 пелагических траловых станций, выполненных в 160 экспедициях ТИНРО-центра с 24 декабря 1979 г. до 30 ноября 2005 г. в северо-западной части Тихого океана и трех сопредельных морях (общая площадь акватории более 6 млн км2), оценена средняя индивидуальная масса особи (W, кг/экз.) всей пелагической макрофауны всего региона в целом, а также различных водоемов, различных групп животных и различных слоев пелагиали по отдельности; исследована зависимость оценок W от пространственных масштабов осреднения данных и различных характеристик объема выборки; рассмотрена связь W с другими интегральными показателями; выяснены особенности ее пространственного распределения, а также специфика ее сезонной и многолетней динамики в 4 бассейнах. Sample size increasing does not cause any regular displacement of average individual weight (W), but accuracy of its estimation grows. However, it is very slow growth: for example, to enhance the accuracy of W estimation on 20 %, the sample size should be enlarged twice in number of individuals or in four times in their biomass. The reason is very high spatial-temporary variability of W for pelagic inhabitants because of mutual influence of many factors, as reproduction, mortality, horizontal and vertical migrations, growth rate, and physiological changes of various species, and also because of methodic aspects of W calculation. So, actual accuracy of W estimation is considerably lower than accuracy of other integrative parameters, and there are no ways for its enhancing in visible future. Therefore all patterns described here are more qualitative than quantitative. The average W value decreases with increase of the area of averaging: average individual weight for a station is higher than that one for a one-degree square, the average individual weight for a biostatistical area is even smaller, and that one for a region (sea) is the smallest. The scope of W variation reduces with the area increasing, too. Apparently, this is the result of smoothing the small-scale spatial heterogeneity of this parameter, more expressed for active swimmers fish and squids and less expressed for crustaceans and macroplankton. As other integrative parameters, W for combined ecological groups is determined by the most numerous representatives: macroplankton by jellyfishes, nekton by fishes, and W for the whole macrofauna is also determined by fishes. Cephalopods have lower influence on W of nekton, and the influence of crustaceans is the least. Widely known Bergmann rule of W spatial distribution is inapplicable to pelagic macrofauna of the North-West Pacific. In ascending order, the average W changes in subsequence: Bering Sea, Okhotsk Sea, Japan Sea, North-West Pacific. Detailed analysis of its distribution shows the absence of latitudinal gradient for the size of water organisms that is basically replaced with circum-continental zonality. In direction from the center of Ocean to its periphery, both primary production and variability of animal size increase, with a tendency of large-sized individuals prevalence, therefore the average individual weight increases, too. As it is shown in previous papers of the author, this tendency is accompanied by decreasing number and biomass of individuals, as well as species diversity and equitability i.e. by numerical and weight domination of few abundant species. In spite of growing size of overwhelming majority of organisms in direction from centre to periphery of the Ocean or from the southeast to the northwest, the largest and rather rare of them meet more often far from the coasts, i.e. among small ones. They are big sharks, tunas, marlins and sunfish rather scanty giants, which rummage extensive oceanic spaces or filter huge volumes of water to provide their livelihood in oligotrophic conditions of "water deserts". Vertical distribution of W could be partially explained by water productivity. High productivity is favorable for living closer to the sea surface, but conditions are unstable in the surface layer. Accordingly, variability of size/weight is increased upward, especially in the epipelagic layer (upper 200 m), and reaches the maximum at the sea surface, where the animals with body weights from decigrams to hundreds of kilograms live. On the contrary, the large depths (mesopelagic layer) are populated basically by medium-sized individuals with body weight from tens to hundreds grams. The average weight of individuals follows to primary production and increases in directions from depth to the sea surface and from center of the Ocean to its periphery, and weight-dependent parameters, as the average individual level of metabolism, individual amount of consumed resources, capacity and mobility of individuals, and the share of predators, grow in the same directions. Spatial and temporal distribution of all these parameters is characterized by negative correlation between W and number of individuals (N). Correlation between species richness S and W is mediated by N: there are very few species in conditions of small density this situation corresponds to rarefied oceanic deserts; but S is also low at high density, i.e. in congestions which are monospecific, as a rule. From the other hand, the largest (massive) animals live usually on sites with rarefied population, but the smallest (light) individuals prevail in dense congestions*. That's why the maximum S is observed at middle W values. This is the necessary, but not the sufficient condition: at the same middle W value the number of species can be a few as well, but never is great if large or small individuals prevail. Temporal fluctuations of the average weight depend on any change of size-weight structure of all populations living in a water area, their migration activity, feeding, growth, reproduction, or mortality. Some populations depend on the same factors equally, others differently, the third react to other factors at all. Sets of species-specific wave processes suppress or strengthen each other because of density factor, competition, predation and other biotic interrelations. The summary or average W fluctuation is a complex result of huge number of multidirectional changes. Nevertheless, the temporal W variability conforms completely to the rule of negative correlation between W and N. Both seasonal and long-term fluctuations of W occur almost precisely in antiphase to the N fluctuations, so far as both ones are determined by dynamics of size-weight structure for the most abundant populations. Annual variability of W is connected mainly with the processes of growth and reproduction, its other important reason is wintering migrations caused by higher tolerance of large individuals to low temperatures they leave the periodically cooled water layers later than small ones and come back earlier. Long-term fluctuations of W are connected with community reorganization: almost everywhere the periods of pollock or sardine domination were replaced by epochs of smaller alternative species. After inevitable recession of the modern wave of high salmons abundance, the process of pelagic macrofauna becoming smaller will obviously continue, and new growth of W is not expected in the foreseeable future.