Is size at sex transition an indicator of growth or abundance in pandalid shrimp?

Length at sex transition in northern shrimp (Pandalus borealis) off West Greenland in relation to changes in temperature and stock size

“…It appears therefore reasonable to conclude that the prominent cause for the decrease in length at sex change of northern shrimp in West Greenland waters in the recent years was temperature-dependent growth, and, similar to observations on the impact of environmental effects on the size at sex change of northern shrimp on the Nova Scotian shelf reported by Koeller et al (2000Koeller et al ( , 2003, no evidence was found that males actively regulate their size at sex transition depending on female density to compensate for a decrease in reproduction potential as suggested by sex allocation theory according to Charnov (1982) and Charnov and Anderson (1989). Koeller et al (2003) stated that a constant ratio of length at sex transition and maximum length attainable as proposed by Charnov and Skúladóttir (2000), coupled with the positive relationship between female size and fecundity, which has been documented for several stocks of northern shrimp (Shumway et al, 1985;Bergstrøm, 2000), implies that a decrease in size at sex change would have a negative effect on population reproductive capacity. However, Skúladóttir et al (1991) reported that northern shrimp at Iceland spawns only every second year in offshore areas where the near-bottom temperature is low compared to inshore areas in which the females spawns every year, and northern shrimp may compensate for a decreased reproductive potential due to sex transition at a smaller size through an increase of average female spawning frequency, i.e.…”

“…However, Charnov and Skúladóttir (2000) demonstrated for northern shrimp in Icelandic waters that length at sex transition and maximum length that individuals attain in the population are closely related and that its ratio of 0.8 is approximately invariant. This may imply that northern shrimp undergoes a terminal molt sometime after maturation of the female and means that, coupled with a positive relationship between female size and fecundity (Shumway et al, 1985;Bergstrøm, 2000), a decrease in length at sex transition would have a negative effect on population reproductive potential (Koeller et al, 2003). Skúladóttir and Pétursson (1999), Koeller et al (2000), and Hansen and Aschan (2000) reported effects of temperature and stock size on the length at sex transition for northern shrimp in Icelandic waters, on the Nova Scotian Shelf and in the Barents Sea, respectively.…”

Decreasing shrimp (Pandalus borealis) sizes off Newfoundland and Labrador – environment or fishing?

“…Biologically, a decrease in the mean size of female shrimp could have a significant effect on the population's reproductive capacity, as size is directly related to fecundity (Shumway et al, 1985). Decreased size at transition from male to female for this protandric shrimp hermaphrodite has been hypothesized to be a response to fishing (Charnov, 1981), but it has also been attributed to environmentally-caused or densitydependent changes in growth rate (Koeller et al, 2000(Koeller et al, , 2003. The latter is a plausible explanation for the Newfoundland stock, which has been increasing in biomass for a number of years due to release of predation pressure and/or a favourable physical environment (Lilly et al, 2000).…”

“…, 1985). Decreased size at transition from male to female for this protandric shrimp hermaphrodite has been hypothesized to be a response to fishing (Charnov, 1981), but it has also been attributed to environmentally‐caused or density‐dependent changes in growth rate (Koeller et al. , 2000, 2003).…”

Distribution and reproductive aspects of the pandalid shrimp,Pandalus eous,in the deep sea of the East Sea, Korea

“…Bergströ m (2000) reported that shrimp of the genus Pandalus have attracted considerable scientific interest, mainly due to two reasons: their commercial value and reproductive strategy. The Northern shrimp Pandalus eous also attracted special interest because of its protandric life cycle, and as the target of important fisheries in the North Pacific (Koeller et al 2000: Koeller et al 2003Ouellet 2005). In the Japan Sea, sex reversal of P. eous begins in July, spawning occurs in April, and hatching out takes place between February and March (Nakame 1991).…”