First insight into personality traits in Northern pike (Esox lucius) larvae: a basis for behavioural studies of early life stages

Personality traits have been studied for some decades in fish species. Yet, most often, studies focused on juveniles or adults. Thus, very few studies tried to demonstrate that traits could also be found in fish larvae. In this study, we aimed at identifying personality traits in Northern pike (Exos lucius) larvae. Twenty first-feeding larvae aged 21 days post hatch (16.1 +/− 0.4 mm in total length, mean +/− SD) were used to establish personality traits with two tests: a maze and a novel object. These tests are generally used for evaluating the activity and exploration of specimens as well as their activity and boldness, respectively. The same Northern pike twenty larvae were challenged in the two tests. Their performances were measured by their activity, their exploratory behaviour and the time spent in the different arms of the maze or near the novel object. Then, we used principal component analysis (PCA) and a hierarchical ascendant classification (HAC) for analysis of each data set separately. Finally, we used PCA reduction for the maze test data to analyse the relationship between a synthetic behavioural index (PCA1) and morphometric variables. Within each test, larvae could be divided in two sub groups, which exhibited different behavioural traits, qualified as bold (n = 7 for the maze test and n = 13 for the novel object test) or shy (n = 9 for the maze test and n = 11 for the novel object test). Nevertheless, in both tests, there was a continuum of boldness/shyness. Besides, some larvae were classified differently between the two tests but 40 % of the larvae showed cross context consistency and could be qualified as bold and/or proactive individuals. This study showed that it is possible to identify personality traits of very young fish larvae of a freshwater fish species.

The French Polynesian experience

French Polyncsia is currently the world's largest producer of cultured black pearls with exports worth US$150 millions annually. The activity has become of prime socio-economic importance the archipelagos with strong support and control of the government. In the mid-1980s, mass mortality of the black-lipped pearl oyster, Pinctada margaritifera, has occurred in several atolls and challenged the development of pearl farming activity. Consequent Studies and surveys have described severa! pathologica! conditions. None of those is considered to pose significant threat to the industry. However, they are monitored by a surveillance program in order to prevent and control emerging diseases. The governmemt of French Polynesia has developed efforts to maintain high quality of the pearls and sustain demand of the markets. This paper reviews a successful model of development based on proactive policy and cooperation among stakeholders.