Invasive species sustain double-crested cormorants in southern Lake Michigan

Abstract

Double-crested cormorants (Phalacrocorax auritus) have long and often been implicated in having detrimental effects on fisheries. Resulting persecution, as well as DDT water contamination, led to a major decline of the species throughout its range. Research shows that the main components of cormorant diets vary significantly among forage, invasive, or economically important fish species. A recent, rapid increase in cormorant abundance in the Great Lakes has led, in some instances, to calls for the management of cormorant populations.Thus the objective of this study was to determine the prey composition of the double-crested cormorant colony in East Chicago, Indiana. This study builds on previous work in the north basin of Lake Michigan by focusing on cormorant diet composition at their only significant nesting colony in the southern basin where cormorant diet has been unstudied. Regurgitated pellets were collected from the colony and diagnostic bones were used to elucidate diet composition. Alewife (Alosa pseudoharengus), round goby (Neogobius melanostomus), Lepomis spp., white perch (Morone americana) and yellow perch (Perca flavescens) were the most frequently found prey items depending on cormorant breeding stage. Invasive species (i.e., alewife, round goby, white perch) contributed over ninety percent of the individuals and eighty percent of the biomass to cormorant diet over the study period. No salmonine species were detected suggesting that negative effects on this important fishery would likely occur only via direct competition for prey (e.g., alewife). Predation on yellow perch, which occurred mainly prior to and during the perch spawning season (i.e., of age-1 and older individuals), may warrant further study to quantify the effects on the local recreational yellow perch fishery. However, because yellow perch abundance is thought to be currently limited by poor recruitment at age-0, these results do not support active management of the cormorants at this colony to protect local fisheries. NORTHERN

Endemic Lake Baringo Oreochromis niloticus fishery on verge of collapse: Review of causes and strategies directed to its recovery, conservation and management for sustainable exploitation

“…aethiopicus and C. gariepinus , which currently constitute a higher proportion of fish landings, are too large for the birds to swallow. This suggestion corroborates well with the observations by Madula and Jones (2016) who reported in their study on invasive species sustaining double‐crested cormorants in southern Lake Michigan that small‐bodied invasive fish species such as round goby ( Neogobius melanostomus ), white perch ( Morone Americana ) and alewife ( Alosa pseudoharengus ) constituted over 80% and 90% of the diet of cormorants by biomass and number, respectively. Thus, because of the stunted growth of O .…”

“…The birds had spread around the lake in 2015, with a new habitat of dead trees left from the flooded lake being a foraging site. While this cormorant invasion is new to Lake Baringo, this bird species is known to cause problems to various fisheries around the world (Madula & Jones, 2016). Recent observations, however, suggest a majority of the greater cormorants are exiting from Lake Baringo, possibly attributable to fishery that is less attractive as a foraging site.…”

Exploring potential effects of cormorant predation on the fish community in Saginaw Bay, Lake Huron

“…The large contribution of Notropis spp. and gizzard shad (during fall) in the Saginaw Bay cormorant diets is consistent with this, and the prevalence of round goby in the diet is similar to other areas in the Great Lakes (Somers et al, 2003;Coleman et al, 2012;Johnson et al, 2010Johnson et al, , 2015aVan Guilder and Seefelt, 2013;Madura and Jones, 2016).…”

“…Because Saginaw Bay is a valuable recreational and commercial fishing location , cormorants on Sportfish were not the dominant diet item by number or biomass except in April 2013 when yellow perch (almost all age-1) were the dominant component (biomass and number) of the diet at Little Charity Island and in June 2013 when walleye comprised 54% of the diet biomass at Spoils Island. Yellow perch consumption occurred mostly in April and early May, a pattern which has been found in other areas of the Great Lakes (Diana et al, 2006;Madura and Jones, 2016). However, in Saginaw Bay the consumption during early spring was not of spawning adults, but of age-1 fish.…”

Reconstructing Long-Term Changes in Avian Populations Using Lake Sediments: Opening a Window Onto the Past

“…With these data, it is possible to estimate the historical size of cormorant populations and also consider the differences in the new environment driven by increasing anthropogenic influence, which together can be used to help set informed and achievable management goals. Although paleolimnological data suggested that the current double-crested cormorant population in Lake Ontario is now more numerous than in the past ∼150 years, the large colonies are principally supported in the new environment by introduced and nuisance warm-water fish species that are growing in numbers due to climate change, such as round goby (Neogobius melanostomus) and alewife (Alosa pseudoharengus) (Madura and Jones, 2016). By preying on these warm-water fish species, it could be argued that cormorants act as a biological control that contributes to maintaining natural biodiversity and supports commercially valuable native cold-water taxa, such as lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) (Johnson et al, 2010(Johnson et al, , 2015.…”