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Sex-specific nutritional requirements for crude protein and fat were demonstrated in cultured (F1) Penaeus stylirostris brood stock. Female shrimp required diets which had higher protein (32 versus 27%), lower fat (2.5 versus 3.9%), higher protein/calorie ratios (8.5 versus 6.8% protein/kcal/g), and much higher protein/fat ratios (15.4 versus 7.8% protein/% fat) than males. These studies have also demonstrated a nutritional demand corresponding to the onset of ovarian maturation, a phenomenon which was explained as a reduction in growth rates at the attainment of 30 to 35 g in shrimp fed deficient diets. Both the quality and the quantity of dietary fat were shown to affect the growth of P. stylirostris brood stock. Male growth was positively correlated with the quantity of eicosapentaenoic acid (20:5 ω3) in the diets. The females were not affected by the types of fatty acids in the fat; they were influenced more by the quantity of fat, i.e., as the fat level of the diet increased, the growth decreased. Cold extrusion feed (CEF) diets supplemented with squid, and diets which included squid as one of the ingredients in the formulation, were found to stimulate better growth in both male and female brood stock as compared to CEF diets of equal protein and fat content without squid. The protein/fat ratio, as well as the content of polyunsaturated fatty acids (PUFA), were suggested to be responsible for the improved growth. Comparisons were made between the quality of spawns from wild P. stylirostris matured in captivity (P1) and F1 shrimp. Protein levels of the eggs did not correlate with either the number of eggs spawned or the eclosion rate. The number of the eggs spawned was correlated positively with the levels of eicosaenoic acid (20:1 ω9) in both P1 and F1 eggs, and correlated negatively with linoleic acid (18:2 ω6) in P1 eggs only. Spawning times were reported to occur later in the evening as summer approached. A significant, negative correlation was observed between the elapsed time from copulation, i.e., collection of fertilized shrimp, to spawning and eclosion rate. Also, a significant positive correlation was observed between the number of spawns which contained eggs which did not hatch, and the elapsed time from copulation to spawning. The number of eggs spawned and the eclosion rate were found to be higher in P1 shrimp as compared to F1 shrimp. Also, first breeding season spawners (FBS) had better quality spawns than second breeding season (SBS) spawners, i.e., more eggs with higher eclosion rates. A general reduction in the quality of the spawns was therefore implicated as a result of the culture conditions. Multiple spawning behavior was observed and there appeared to be no qualitative or quantitative difference between spawns. Tank size and shape were demonstrated to affect the onset of ovarian development and the transfer of the spermatophore. A minimum of three meters was thought to be required for the development of the ovaries and the successful transfer of the spermatophore.

Demographic parameters and the general biology of the subantarctic shrimp Nauticaris marionis from the Prince Edward Islands were investigated. The carapace length is the most accurate indicator of body size and it was confirmed that N. marionis is a partially protandric hermaphrodite. Gravid females of N. marionis observed mainly in March with negligible hatching persisting until April/May. The majority of juveniles develop into males. Juveniles are characterised by an appendage on the endopodite of the first pleopod called the appendix interna or a.i.1. Juveniles that develop into males do so by growing a further appendage on the endopodite of the second pleopod. This appendage characterises males and is called the appendix masculina (or a.m.). Juveniles may develop directly into primary females through the development of an ovary and the loss of the a.i.1. The sequence differs among individuals, with some developing the ovary before losing the a.i.1 and others losing the a.i.1 first. Loss of the a.i.1 appears to be by shedding during a single moult, rather than by atrophy. Females can also develop by an alternative route as secondary females. Such animals first become males with an a.m. and then develop an ovary, thus forming an intermediate form called a tertium quid, or “third thing”. Again, there are two forms of tertium quid. Tertia quae a have the a.m. as well as the a.i.1. Tertia quae b have the a.m. in combination with an ovary but no a.i.1. Either form of tertium quid can develop into a secondary female through loss of the a.m., and in the case of the tertium quid a, loss of the a.i.1. It is unclear whether sexual differentiation occurs in the plankton or just after N. marionis settles on the benthos. The results of gut content analysis suggest that N. marionis is an opportunistic feeder, preying on a variety of prey with a preference for detritus, benthic amphipods and gastropods. Cannibalism of conspecific pleopods by large individuals of N. marionis occurred mostly in females, particularly in incubation containers. Cannibalism also occurs in males, and its occurrence depends on individual size, not gender. No diel patterns were observed in the feeding activity of N. marionis. In situ daily rations of males (carapace length <7mm) and females (>7mm) were equivalent to ≈10% and ≈5% of body dry weight, respectively. The von Bertalanffy growth curve parameters were empirically identified, by cohort analysis of data collected during 4 years, as K = 0.22239/year, L[subscript]∞ = 14.05789mm, t₀ = -0.05174, L₀ = 0.16083mm. N. marionis can survive up to seven years under natural conditions.