Training camp—A way to improve survival in European lobster juveniles?

Ann-Lisbeth Agnalt,Ellen Sofie Grefsrud,Eva Farestveit,Knut Eirik Jørstad

doi:10.1016/j.fishres.2016.09.021

Ann-Lisbeth Agnalt, Ellen Sofie Grefsrud + Show 2 more

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https://doi.org/10.1016/j.fishres.2016.09.021

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Journal: Fisheries Research	Publication Date: Oct 7, 2016
Citations: 12	License type: cc-by

Affiliation: Norwegian Institute of Marine Research

Abstract

A series of experiments was conducted to test if keeping hatchery-produced European lobster juveniles (Homarus gammarus) in an enriched environment with substrate and shelter would improve anti-predator behaviour and survival in a competition setting. Newly hatched postlarvae (stage IV) were divided into two treatments. Naïve postlarvae were raised in single compartments, while trained postlarvae were released communally into tanks with substrate and shelter, allowing for developing burrowing and shelter-seeking behaviour and interactions with conspecifics. The duration of the treatment lasted 181days in 2007/2008 and 226days in 2008/2009. In the second experiment, 4-mo old juveniles were purchased from a commercial hatchery and divided into the same two treatment groups. The treatments were considerably shorter, lasting 47days. At the end of the treatment period an equal number of juveniles from each treatment was released into experimental units with substrate and shelter i.e. semi-natural system for a period of 91–145days. Number of shelters was half the total number of juveniles to induce competition for shelters. In both experiments, trained juveniles occupied more shelters and had higher survival than naïve juveniles. Combining all experiments, average survival was 53% in trained lobsters compared with 18% in the naïve lobsters. These results are the first to demonstrate that enriching the hatchery environment for a period of time (a minimum of 47days here) while rearing European lobster juveniles increased their shelter occupancy and their survival compared to naïve juveniles the same size and age. Survival rates were 3–4 times higher in trained compared to naïve lobsters after 145days.

Highlights

Efforts to increase recruitment to the fisheries by releasing hatchery-produced juvenile fish or invertebrates have been made for more than 150 years (Munro and Bell, 1997; Nicosia and Lavalli, 1999; Bell et al, 2005)
We found that training European lobster juveniles resulted in increased shelter occupancy and survival, compared with naïve juveniles
Our results demonstrate that experience of environmental complexity and social interactions increases shelter-seeking ability and survival in hatchery reared European lobster juveniles

Summary

Introduction

Efforts to increase recruitment to the fisheries by releasing hatchery-produced juvenile fish or invertebrates have been made for more than 150 years (Munro and Bell, 1997; Nicosia and Lavalli, 1999; Bell et al, 2005). In Norway, hatchery-produced lobster juveniles released over a period of 5 years and monitoring the fishery for 10 years resulted in an overall recapture of 6.2%, ranging from 3.6 to 9.1%, for the various year classes (Agnalt et al, 2004). This is rather high compared with many other release programs, but Borthen et al (1999) made an economical analysis on these data and concluded that the recapture rate must be higher than 14% to break-even. This is in accordance with economic estimates by Moksness et al (1998)

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