Sex‐specific food intake in whiting Merlangius merlangus

Abstract

In this study, the topic of sexual growth dimorphism in whiting Merlangius merlangus is examined. To understand the magnitude and underlying mechanisms, North Sea International Bottom Trawl Survey (IBTS) data and two additional datasets from the third quarter of 2007 and the first quarter of 2012 were analysed. Merlangius merlangus displays distinct differences in growth parameters between males and females, with females reaching a higher asymptotic length (L∞ ) than males. To identify the mechanisms which lead to higher growth in females, the quantity and the quality of the diet of M. merlangus in the North Sea were investigated to compare the sex-specific energy uptake levels. The diet composition did not differ between the sexes, but females had higher stomach content masses than males of the same total length (LT ), and showed lower proportions of empty stomachs. Moreover, female M. merlangus had higher liver and empty stomach masses compared with males of the same size, which indicates additional sex-specific differences in the metabolic costs and energy allocation patterns. Finally, interannual differences were found in the stomach contents, the share of empty stomachs and liver masses of M. merlangus in the North Sea.

The diet of whiting Merlangius merlangus in the western Baltic Sea

“…Thus, the lower growth observed in the western Baltic Sea may be associated with lower mean stomach content mass. In the southern North Sea, lower mean stomach content masses coincided with lower mean L T at age in 2007, and the opposite was seen in 2012 (Lauerburg et al , ). Furthermore, males had lower growth rates, lower stomach content masses and higher proportions of empty stomachs than females (Lauerburg et al , ).…”

“…In the southern North Sea, lower mean stomach content masses coincided with lower mean L T at age in 2007, and the opposite was seen in 2012 (Lauerburg et al , ). Furthermore, males had lower growth rates, lower stomach content masses and higher proportions of empty stomachs than females (Lauerburg et al , ). In the present study, males in the western Baltic Sea had higher proportions of empty stomachs compared to females, but the mean stomach content masses were not significantly different.…”

Growth and food consumption of whiting Merlangius merlangus

“…Timing of hatching and larval size may influence the growth trajectory of the first year and potentially the lifetime growth as seen in G. morhua (Paulsen et al ., ). Differences in hatching date and larval size probably result in large variation in mean length at age, which is also supported by the substantial overlaps in length ranges between adjacent age groups (Bowers, ; Flintegaard, ; Gambell & Messtorff, ; Keyl et al ., ; Lauerburg et al ., ). High initial growth rates are often seen and it is not uncommon for individuals to attain a size of 20 cm in total length ( L ) by the end of their first year (Armstrong et al ., ; Bowers, ; Flintegaard, ; Hillis, ; Lauerburg et al .…”

“…High initial growth rates are often seen and it is not uncommon for individuals to attain a size of 20 cm in total length ( L ) by the end of their first year (Armstrong et al ., ; Bowers, ; Flintegaard, ; Hillis, ; Lauerburg et al . , ).…”

“…Merlangius merlangus (L. 1758) is an important piscivorous fish throughout the north‐east Atlantic Ocean, where it preys upon commercially valuable fish taxa such as ammodytids, clupeids and gadoids (Hislop et al ., ; Lauerburg et al ., ; Ross et al ., ). Total consumption rates estimated for M. merlangus in the North Sea (NS) in the 1980s suggest that the species exert a considerable predation pressure on Norway pout Trisopterus esmarkii (Nilsson 1855), lesser sandeel Ammodytes marinus Raitt 1934, sprat Sprattus sprattus (L. 1758) and herring Clupea harengus L. 1758 (Hislop et al ., ).…”