Biology and Physiology of Feeding in Adult Lampreys

Abstract

Although landlocked sea lampreys (Petromyzon marinus) attack all but a few of the smallest teleosts in the Great Lakes, the large cold-water species have received the most predation. Information on the feeding habits of anadromous lampreys is limited, but they probably are not specific in their choice of hosts. Species differences exist in the relative proportions of blood and muscle tissue which are consumed. The landlocked sea lamprey primarily feeds on the blood of host fishes at rates of 3–30% of its wet body weight∙d−1 (10 °C). The estimated gross conversion efficiency for this species feeding ad libitum at 10 °C is 39%. This relatively high efficiency is partly attributable to the nature of their blood diet which results in small fecal energy losses of about 3.4% of intake energy. Maximum growth rates occur at 20 °C for sea lampreys of 10–30 g initial weight and at 15 °C for lampreys of 30–90 g. At all experimental temperatures (5–20 °C), growth rates decline with increases in lamprey weight. Increases in sea lamprey weight and in water temperature up to 20 °C cause the rate of host mortality to rise suggesting that, under natural conditions, mortality is seasonal. Landlocked sea lampreys show a preference for specific areas on their hosts, select larger hosts more frequently, and are not attracted to hosts that have lampreys feeding on them. Such strategies serve to maximize food intake and prolong host survival while ensuring food material of constant energy content.Key words: adult lampreys, feeding, hosts, growth rate, temperature, host mortality, behavior