Density Dependant Sex Change in Northern Shrimp, Pandalus borealis, on the Scotian Shelf

Abstract

We investigated factors affecting sex change in the Pandalid shrimp Pandalus borealis on the Scotian Shelf. Transition from male to female occurred at different sizes and ages, and could not be related to a minimum size or age. Our data did not show a positive relationship between abundance of older females and shrimp size at sex transition, nor a negative relationship between male:female sex ratio and shrimp size at transition, that would be expected if the population was compensating for decreases in reproductive capacity as predicted by sex allocation theory. Size at transition was inversely related to female density, which was attributable to density dependent growth affecting all stages. Density dependant growth also appeared to explain previously reported results which had been used to support sex allocation theory. Density was the most important factor determining individual growth at high densities while at low densities other factors, including temperature, were also an important determinant of growth. We conclude that a decrease in the size at transition can be indicative of a healthy, as well as a declining stock, and must be fully understood before it can be used as an indicator of stock status. Possible alternative mechanisms for regulating sex change in Pandalids are discussed.

Growth Pattern of Pandalus gracilis (Decapoda: Pandalidae) in the Southern Coastal Waters of Korea

“…Previous studies suggested that several factors affected sex changes in pandalid shrimps (Koeller et al, 2000;Chiba et al, 2003;Wieland, 2004;Skúladóttir et al, 2005). According to Wieland (2004) and Skúladóttir et al (2005), the change in size at sex transition in P. borealis was significantly correlated with temperature.…”

“…Our study is consistent with their results. Koeller et al (2000) noted that size at sex transition in P. borealis was inversely related to female density, emphasizing that density was the most important factor determining individual growth at a high population density. Adding another factor, Chiba et al (2003) stressed that male-male com- Fig.…”

Effects of conspecific associations on size at sex change in three species of calyptraeid gastropods

“…Robertson 1972, Alonzo & Warner 2000a,b, Mackie 2003, Perry & Grober 2003, shrimp (see e.g. Charnov 1982, Koeller et al 2000, Chiba et al 2003, and mollusks (e.g. Coe 1953, Hoagland 1978, Charnov 1982, Soong & Chen 1991, 2003.…”

Crepidula Slipper Limpets Alter Sex Change in Response to Physical Contact with Conspecifics

“…An inhibitory influence of conspecifics on sex change has been shown in a variety of taxa (Koeller et al, 2000;Bauer, 2002;Morrey et al, 2002;Baldwin and Bauer, 2003;Baeza, 2007). In coral reef fishes, visual, behavioral, and chemical cues can all influence sex change (Ross et al, 1983;Cole and Shapiro, 1995).…”

“…Sex allocation theory predicts that the optimal size to change sex in sequential hermaphrodites and the optimal allocation to male and female function in simultaneous hermaphrodites depend on the composition of an individual's mating group or local population (Charnov, 1982, and references therein). Field studies using diverse sex-changing taxa have largely borne out these predictions (Hoagland, 1978;Charnov and Anderson, 1989;Collin, 1995;Koeller et al, 2000;Morrey et al, 2002;Baldwin and Bauer, 2003;Schleicherová et al, 2006;Avise and Mank, 2009;Hoch and Cahill, 2012). Intraspecific communication must be involved in these responses to local conspecifics, but the nature of the cues or signals involved, and the mechanisms producing these patterns of optimal sex allocation have not been closely examined in many species.…”