The length and weight of Russian sockeye (Oncorhynchus nerka) returning to the Ozernaya River (Kamchatka) was substantially reduced in years when the ocean abundances of Kamchatkan pink (O. gorbuscha) and sockeye salmon were high. We found that the density‐dependent reduction in sockeye growth on a per‐capita basis was greater for sockeye than for pink salmon. However, the overall effect of pink salmon abundance on sockeye growth was greater because of the higher numerical abundance of pink salmon. The strongest statistical relationships were found for sockeye from separate age groups; pooled data combining all age classes were statistically insignificant. We estimate that, if pink salmon were absent, the most strongly affected age group of sockeye salmon (2.1 males) would weigh twice as much at maturity than if pink salmon populations from eastern and western Kamchatka were both simultaneously at peak observed abundances. Trophic competition in the ocean between pink and sockeye salmon can therefore have a significant influence on the productivity of sockeye populations for the most strongly affected age groups. These effects are large enough that they should be explicitly considered in the management of salmon populations.
SynopsisTwo sympatric morphs of threespine stickleback Gasterosteus aculeatus are found in Lake Azabachije (Kamchatka, USSR); resident low-plated leiurus and completely plated trachurus, migrating from the Bering sea into the Lake to spawn. The absence of the intermediate morph semiarmatus and significant differences in a number of characters are indicative of reproductive isolation. The results show that the leiurus morph is common in the regions other than those with mild climate and small seasonal fluctuations of temperature.
BackgroundConcern about the decline of wild salmon has attracted the attention of the International Union for the Conservation of Nature (IUCN). The IUCN applies quantitative criteria to assess risk of extinction and publishes its results on the Red List of Threatened Species. However, the focus is on the species level and thus may fail to show the risk to populations. The IUCN has adapted their criteria to apply to populations but there exist few examples of this type of assessment. We assessed the status of sockeye salmon Oncorhynchus nerka as a model for application of the IUCN population-level assessments and to provide the first global assessment of the status of an anadromous Pacific salmon.Methods/Principal FindingsWe found from demographic data that the sockeye salmon species is not presently at risk of extinction. We identified 98 independent populations with varying levels of risk within the species' range. Of these, 5 (5%) are already extinct. We analyzed the risk for 62 out of 93 extant populations (67%) and found that 17 of these (27%) are at risk of extinction. The greatest number and concentration of extinct and threatened populations is in the southern part of the North American range, primarily due to overfishing, freshwater habitat loss, dams, hatcheries, and changing ocean conditions.Conclusions/SignificanceAlthough sockeye salmon are not at risk at the species-level, about one-third of the populations that we analyzed are at risk or already extinct. Without an understanding of risk to biodiversity at the level of populations, the biodiversity loss in salmon would be greatly underrepresented on the Red List. We urge government, conservation organizations, scientists and the public to recognize this limitation of the Red List. We also urge recognition that about one-third of sockeye salmon global population diversity is at risk of extinction or already extinct.
Age and length-weight structure of sockeye salmon spawners are considered for the feeding-spawning lakes of southeastern Kamchatka, as Dalneye (1976-2013), Blizhneye (1939-2013), and Listvenichnoye (1999-2013), and for Lake Sarannoye on Bering Island (1990-2013). By these data, the age of sockeye salmon maturing is: 2.2, 2.3 and 3.2 in Lake Dalneye, 1.2, 1.3, 2.1 and 2.2 in Lake Blizheye, 2.2, 2.3 and 3.3 in Lake Listvenichnoye, and 2.2, 2.3, 3.2 and 3.3 in Lake Sarannoye. These age groups dominate in the samples of spawning sockeye with the portion 70-90 %. Long-term dynamics of length and weight of sockeye spawners is distinguished by negative trends significant for the longest time-series in Lake Blizhneye and insignificant for the shorter one in Lakes Dalneye; the length of observations in Lakes Listvenichnoye and Sarannoye is not enough to reveal trends. Besides, cyclic variations with the period 5-10 years could be revealed for the long tome-series. As a rule, each cycle includes the phases of gradual decreasing and sharp increasing of length and weight. Year-to-year dynamics of the length-weight structure in the common period of observations is similar for all investigated lakes.
икр., встречаемость самок -55,3 %. В отличие от нерки ряда рек восточного побережья Камчатки, у нерки р. Жупанова за рассмотренный период отсутствует достоверный меж-годовой негат ивный тренд длины и массы тела.Ключевые слова: возраст, половозрелая нерка, длина и масса тела, плодовитость.
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