Spatial and temporal variability of Biological and Fisheries indicators of a small-scale crustacean fishery in southern Chile.

The evaluation of fisheries status is a challenge especially for small-scale fisheries since most of them are data limited mainly due to scarce budget associate to their low contribution to national Gross Domestic Product. In remote areas, monitoring becomes not only expensive but difficult to derived trends and hence, develops conclusions about the state of the fishery. Metacarcinus edwardsii had become a socio-economically important fishery in the south of Chile that falls under the former description since is an exclusively artisanal fishery mainly harvest in the south of Chile (41°S- 46°S). It is monitored annually under a scheme that allows the registration of biological and fishing information, mainly from the landing ports and secondarily, from fishing grounds. This monitoring strategy have had limitations, especially south of 45°S, since due to remoteness of fishing grounds combined with rough weather conditions, logistic and cost of data collection is difficult and expensive. In this context, data limitation had prevented the development of stock assessments models and so far, monitoring had not allowed detecting spatial and temporal trends associated to biological and fisheries indicators. In the present study we collected data in fishing grounds on board of artisanal vessels south of 45° during an annual cycle. Data collected were used to construct indicators based on catch per unit effort (over and lower minimum legal size), size, sex-ratio and relationship between weight and size. In conjunction, data collection allowed to estimate reproductive indicators that had proven to be vulnerable to local environmental conditions and also due to different degrees of fishing intensity. In this context, results were compared with estimations made for this species in two northern zones (at 36°S and 39°S) which represents comparatively different fishing intensities. The indicators estimated were (1) Size at the onset of maturity, which was estimated associated to physiological and morphometrical sexual maturity of females and males separately; (2) Sperm transference capacity, which was evaluated through Vaso-Somatic and Receptacle-Somatic indices and (3) Fecundity potential, in terms of number of eggs per ovigerous female. Results indicated that seasonal variability influenced biological, and fisheries indicators and some patterns could be concluded between fishing zones. Detected variability was in concordance with reproductive cycle being registered for this species. In this context, a monitoring design should select one or two seasons and zones that should be monitored along a time series to derive statistically significant patterns. The collection of information on board of artisanal vessels allowed the recording of some variables, otherwise no notice. Traps soak time was one variable that was probed to influence estimated indicators hence should be considered not to misinterpret catch and other indicators. Reproductive indicators and cycle showed no differences with latitude. Sperm transference capacity showed no clear latitudinal pattern, in fact presented no differences between low and high fishing intensity zones. The exception was the gonadal size at maturity in males in the southernmost area that where in the lowest range estimated, which in conjunction with low females’ fecundity could be suggesting that the fishery is affecting its reproductive condition. Local environmental adaptations are not ruled out since this area is in the southern range of this species distribution.