Relationship between gill raker morphology and feeding habits of hybrid bigheaded carps (Hypophthalmichthysspp.)

Abstract

Key-words:bigheaded carp, gill raker morphology, filter-feeding, food size, plankton Bigheaded carps and especially silver carp have been considered as an effective biological control for algal blooms, thus were introduced to several countries in the last decades, including Hungary. Our aim was to explore the feeding habits of bigheaded carps in Lake Balaton (Hungary), where the stock consists mainly of hybrids (silver carp × bighead carp). We examined the relationship between filtering apparatus (gill raker) morphology and size-distribution of planktonic organisms in the food. We failed to find any significant relationship between gill raker parameters and plankton composition in the filtered material. Bigheaded carps with various types of gill rakers consumed food within the same size-spectrum, independently of the rate of hybridization. However, the linkage between the proportion of different planktonic size classes in the water and in the diet of fish was detectable in case of both phytoplankton and zooplankton consumption, suggesting that the seasonally variable availability of different food items was an important factor in determining the food composition of bigheaded carps. We can deduce that bigheaded carps consume high amounts of zooplankton to meet their energy requirements, and the diet overlap among bigheaded carps and other planktivores may exert negative effects on native fish populations. RÉSUMÉRelation entre la morphologie des branchiospines et les habitudes alimentaires d'hybrides de carpes à grosse tête (Hypophthalmichthys spp) Mots-clés :carpe à grosse tête, La carpe à grosse tête et en particulier la carpe argentée ont été considérées comme un moyen de contrôle biologique efficace contre la prolifération des algues, ainsi elles ont été introduites dans plusieurs pays dans les dernières dé-cennies, dont la Hongrie. Notre objectif était d'étudier les habitudes alimentaires des carpes à grosse tête dans le lac Balaton (Hongrie), où le stock se compose principalement d'hybrides (carpe argentée × carpe à grosse tête). Nous avons

Making a master filterer: Ontogeny of specialized filtering plates in silver carp (Hypophthalmichthys molitrix)

“…In contrast, the gill rakers of the silver carp diverge early in ontogeny from this stereotypical filtering anatomy as individual rakers stitch together via first epithelium and then bone. The gill rakers are modified into filtering plates that are able to capture, retain, and transport particles as small as 4 μm (Battonyai, ; Cremer & Smitherman, ; Zhou et al, ).…”

“…Nonetheless, there are key anatomical similarities between the adult filtering structures that suggest how the filtering plates of silver carp may have evolved. For instance, previous literature notes that in bighead carp there are “wide” and “narrow” gill rakers, with “wide” referring to gill rakers that have been modified by growth of longitudinal dermal bone (Battonyai et al, ; Fang, 1928; Verigin, ; Walleser et al, ). In our adult bighead specimens, longitudinal dermal bone modified every eighth individual gill raker, a pattern conserved between silver and bighead carp.…”

“…Although initially introduced to help control algal blooms in federal and private fish farms (Cremer & Smitherman, ), silver carp and its sister species, bighead carp, escaped and invaded natural waterways and currently pose a major threat to the Great Lakes (Freedman et al, ; Nico et al, ; Walleser et al, ). Silver carp are planktivorous filter feeders and consume particles from 4 to 20 μm as well as large zooplankton that are around 80 μm (Battonyai et al, ; Cremer & Smitherman, ; Zhou et al, ); efficient consumption of this broad range of particles allows silver carp to outcompete both native vertebrate and invertebrate filter feeders (Freedman et al, ). Competing directly with large native fish, such as paddlefish and gizzard shad, as well as with smaller invertebrate filter feeders, silver carp have the potential to cause enormous damage to native waterways by limiting available resources (Freedman et al, ).…”

“…Based on the developmental patterning of gill rakers in other teleostean fishes, we hypothesize that the gill rakers of silver carp will follow a similar pattern and begin as comb‐like cartilaginous protrusions eventually diverging from that morphology to form fused filtering plates. This fused filtering plate has allowed silver carp to feed on a wide range of particle sizes (Battonyai et al, ; Cremer & Smitherman, ; Zhou et al, ) outcompeting native species, allowing silver carp to become a destructive invasive species.…”

Gut content microbiota of introduced bigheaded carps ( Hypophthalmichthys spp.) inhabiting the largest shallow lake in Central Europe

“…The present bigheaded carp stock in the lake consists mainly of hybrid (bighead carp × silver carp) individuals (Boros et al, 2014;. Surprisingly, these hybrids with various types of gill rakers (intermediate in development between those typical for the parental species) consume food within the same size-spectrum and have very similar diet composition, independently of the rate of hybridization (Battonyai et al, 2015). Despite low productivity and consequently scarce food resources which have advanced as a result of a successful nutrient controlling program in the drainage, bigheaded carps grow intensively in Lake Balaton and their condition factor (the -plumpness‖ of fish) is relatively high compared to other ecosystems (Boros et al, 2014).…”