Feasibility of compensatory growth in early juveniles of "red claw" crayfish Cherax quadricarinatus under high density conditions

Abstract

The aim of this work is to study the feasibility to induce compensatory growth in Cherax quaricarinatus crayfish at an early stage of development under high density, the typical conditions of nursery phase. An advantageous characteristic of this species is the capacity to face temporary starvation, especially at early stages of development. This would help to design feeding strategies avoiding overfeeding, and diminishing operating costs in aquaculture. In this sense, during the last 8 years it was analyzed in this species the application of intermittent feeding, known as unfavorable feeding condition followed by daily feeding (favorable feeding condition). This alternative feeding protocol was used in the present study to trigger compensatory growth. Juveniles weighing 0.07 ± 0.01 g were distributed in 2 feeding regimes: C (control): juveniles fed daily during 60 days, and IF (intermittent feeding): juveniles deprived of food for 4 days and then fed for the following 4 days, these 4 days’ cycles were repeated during the first 20 days, on day 21 they were daily fed until day 60. Juveniles were stocked in each tank under 0.0096 crayfish/cm2 density, and zootechnical and biochemical parameters were evaluated throughout 60 days. A very suitable and similar survival (~ 65%) was maintained between feeding regimes, and the previously unfavorable feeding condition did not promote greater aggression among juveniles. There was a small compensatory response, but no recovery occurred probably because the favorable feeding condition was too short to trigger a strong compensatory response. Hyperphagia and improvement of feed conversion were not observed in juveniles of IF, suggesting that the high density was the key for these primary compensatory mechanisms to be absent. The competition for food, could have affected and changed the priority in allocating energy resources for accelerated growth. Lipids and glycogen content from body mass were strongly depleted after unfavorable feeding condition, but there was almost a 100% recovery during favorable feeding condition. We suggest that this response was detrimental to body mass as a priority and as a strategy for juveniles to extend survival during the ‘double’ nutritional stress caused by intermittent feeding and high density. The applicability of this alternative feeding strategy during an intensive production system can be viable, however, some changes must be considered in order to trigger compensatory growth. We suggest that a long-term of the favorable feeding condition could trigger a strong compensatory response if the high density tested in the study is maintained. We believe that juveniles of the current study had to face two nutritionally stressful factors: food restriction and high density. This could change the priority in allocation of energetic reserves and then the other suggestion would be to reduce the density if the same alternative feeding protocol is maintained.