Impact of Double-Crested Cormorant Predation on the Yellow Perch Population in the Les Cheneaux Islands of Michigan

The Michigan Department of Natural Resources, in conjunction with the University of Michigan and the U.S. Fish and Wildlife Service, initiated a research study to determine the impact of double-crested cormorants (Phalacrocorax auritus) on the yellow perch (Perca flavescens) population in the Les Cheneaux Islands area of northern Lake Huron. Aerial and nesting colony counts were conducted to monitor cormorant abundance. Creel census counts and tagging of 8,400 perch were used to study perch abundance. We collected 373 cormorants to study food habits via stomach-content analysis. We found that (1) cormorants fed heavily on yellow perch in early spring, but over the entire season only 10 percent of their diet was perch; (2) alewives (Alosa pseudoharengus) and sticklebacks (Culaea inconstans, Pungitius pungitius, Gasterosteus aculeatus) made up the major portion of the cormorants’ diet; (3) cormorants removed only 2.3 percent of the available perch biomass (v. 1.8 percent by anglers over the same period); (4) most fish taken by cormorants were less than 150 mm long; (5) total annual perch mortality was about 45 percent, of which less than 9 percent was due to cormorants; and (6) cormorants accounted for only 0.8 percent of the mortality of legal-size perch (≥178 mm), whereas summer sport fishing accounted for 2.5 percent. Thus, although the impact of cormorants on the perch population may vary slightly from year to year, we conclude that cormorant predation had minimal impact on the local perch population

Beyond the Paradigm: Novel Functions of Renin-Producing Cells

The juxtaglomerular renin-producing cells (RPC) of the kidney are referred to as the major source of circulating renin. Renin is the limiting factor in renin-angiotensin system (RAS), which represents a proteolytic cascade in blood plasma that plays a central role in the regulation of blood pressure. Further cells disseminated in the entire organism express renin at a low level as part of tissue RASs, which are thought to locally modulate the effects of systemic RAS. In recent years, it became increasingly clear that the renal RPC are involved in developmental, physiological, and pathophysiological processes outside RAS. Based on recent experimental evidence, a novel concept emerges postulating that next to their traditional role, the RPC have non-canonical RAS-independent progenitor and renoprotective functions. Moreover, the RPC are part of a widespread renin lineage population, which may act as a global stem cell pool coordinating homeostatic, stress, and regenerative responses throughout the organism. This review focuses on the RAS-unrelated functions of RPC - a dynamic research area that increasingly attracts attention