Marine Biology (in press)
Importance of the Japanese anchovy Engraulis japonicus to breeding rhinoceros auklets Cerorhinca monocerata on Teuri Island, Sea of Japan.
Takahashi A, M Kuroki, Y Niizuma, A Kato, S Saitoh, and Y Watanuki.
Temporal variation in the diet and chick growth of rhinoceros auklets Cerorhinca monocerata, on Teuri Island, Sea of Japan, was studied to understand how local marine environmental changes affect the reproduction of this piscivorous seabird. The food delivered by parents to chicks was sampled every 1-2 week late May to July, 1994 - 1998. Overall, the diet of nestling rhinoceros auklets consisted of (by mass) 61 % Japanese anchovy Engraulis japonicus, 18 % Japanese sand lance Ammodytes personatus, 18 % Japan Sea greenling Pleurogrammus azonus, 2 % other fish and 1 % squid. Among years, the contribution of anchovy ranged from 16 - 93 %. Once anchovy occurred in the diet, it dominated (80 % on average) thereafter. Accordingly, when anchovy appeared early in the diet (1994, 1998), the contribution of anchovy overall was large. First presence of anchovy in the diet late in summer (1997) was possibly related to negatively anomalous sea-surface temperature. Food loads composed of anchovy (34.0 g) were heavier than those of sand lance (22.5 g) and greenling (28.5 g). The energy density of anchovies also was higher: 6.3 kJ/g wet mass compared to 0+ greenling (4.78 kJ/g) and 0+ sand lance (3.78 kJ/g). Thus, a high proportion of anchovy in the diet resulted in high food load mass, high daily growth rates of chicks and high fledging success. This study highlighted the importance of the arrival timing of migratory high-lipid prey, which is influenced by the local oceanographic conditions, to the reproductive performance of a piscivorous seabird.
BD01-4
|
