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The recruitment rate of anchovy in the Peru–Chile upwelling system was studied by testing sensitive to environmental variability when the spawning stock is low in abundance. Times series of sea surface temperature, salinity, depth of the 15 °C isotherm, the upper limit of the oxygen minimum zone, upwelling indices, the Southern Oscillation Index, and indices El Nino 1+2 and El Nino 3.4 were summarized trough Principal Component Analysis (PCA). The first PCA (PC-I) explained 57% of variance and was related to interannual variability driven by the El Nino-Southern Oscillation. The second Principal Component explained 15% of variance and was linked to upwelling indices. Anchovy recruitment rate anomalies were correlated with PC-I scores on the basis of a 6-year-moving-window and accumulated correlation as time progressed. Significant correlation coefficients were found when the spawning stock biomass was low in abundance before 1990. Once sufficient spawning biomass was accumulated (after 1990), the stock was less sensitive to environmental variability. Thus, sensitivity to environmental changes in anchovy, and probably in other small pelagic fishes, is stock-size dependent. This is a key aspect to be considered in the management of transboundary fish stock shared between Chile and Peru, upon current efforts to develop an ecosystem approach to fisheries management.

Chemistry in material laid down prior to capture along the edges of otoliths of Chilean jack mackerel (Trachurus murphyi) showed strong spatial heterogeneity corresponding to hydrographic structure across putative population boundaries between (i) the western and eastern South Pacific Ocean, and (ii) Chile and Peru. Yet the chemistry of the otolith nucleus, in material laid down during early life, showed no evidence supporting the existence of these boundaries. Instead, jack mackerel from New Zealand had similar nucleus chemistry to most sampling areas off South America; and those off southern Peru showed similar nucleus chemistry to most sampling areas off Chile. Strong differences were found between southern and northern Peru, and cluster analysis indicated this was caused by a group of fish off northern Peru with chemistry found nowhere else. Most other fish grouped in two clusters, which showed properties suggesting correspondence with a major spawning zone in oceanic water off central Chile, and a smaller area in coastal water off northern Chile, characterized by similar sea surface temperature, lack of westward transport, and low kinetic energy. Rather than discrete populations separated by boundaries, these results suggest complex spatial structure defined by environmentally mediated survival and connectivity: fish caught off New Zealand may be of South American origin; the spawning zone off central Chile may supply fisheries around the South Pacific; and spawning off northern Chile may be an important source of fish caught locally and in Peru. However, northern Peru does not supply areas further south.

In this study, we review the relationship between female size and spawning frequency using information from Sardinops sagax and Engraulis ringens, two species which are important for the economy of countries located in the Humboldt Current System. We test the hypothesis that spawning frequency is positively related to female size using information for these two species in northern Chile. The data analyzed were obtained from four different sources: (a) reproductive information obtained from the application of the Daily Egg Production Method (DEPM) in E. ringens between 1992 and 2005; (b) adult reproductive parameters for different species of the genus Engraulis; (c) spawns counts for a brood stock of E. ringens reared in captivity; (c) results from an indirect method based on a gonadosomatic calibrated index developed for S. sagax utilizing data obtained from 1974 to 1996. An analysis of the 11-year DEPM data series for E. ringens suggest that the daily spawning fraction also increases with the average weight of mature anchovy females and that such relationship may also be described using an asymptotic model. A plot of the daily spawning fraction and average female weight data obtained from results of DEPM applications for different Engraulis species from around the world also showed a positive correlation, suggesting that this relationship may be valid for many species, even those located in different habitats. An analysis of the data obtained from the E. ringens brood experiments showed that the number of eggs spawned in the tank increased monthly as female age increased, even though the number of females decreased due to natural mortality. Results in S. sagax females showed that smaller females have shorter spawning periods and a lower spawning fraction; accordingly, bigger females spawned more frequently than smaller ones. The long term estimation (1974–1996) of spawning numbers in relation to S. sagax female size was well described by a sigmoid function. © 2007 Elsevier B.V. All rights reserved.

Interdecadal versus interannual time- scale variations of catch data of three anchovy fisheries distributed in the Humboldt Current System (HCS) were analyzed during the period 1960-2002, by using first a loess smoother. The loess residual data were considered as the interannual variation. Interdecadal changes were highly coherent for the three fisheries of anchovy distributed in the HCS, while there were differences in terms of interannual variations. The north-central Peru fishery was similar to the south Peru-northern Chile fishery in terms of the interannual component of fluctuation of these fisheries which was significantly and negatively related with El Nino-Southern Oscillations events occurring during the spring of the previous year. Interdecadal synchronous variations in the three anchovy fisheries suggest a common forcing by long-term environmental factors in the HCS, although other causes cannot be excluded. During the last 40 years, coherent changes in anchovy fisheries were observed, and this synchronous pattern is out of phase with large-amplitude sardine regimes. Long-term climate variability seems to be the main cause for interdecadal fluctuations in anchovy fisheries in the HCS, although available time series are too short to prove this link and exclude the hypothesis of nonenvironmental forcing. Large-amplitude regime shifts may be more important to consider than interannual changes since they can affect simultaneously and more dramatically the three anchovy fisheries distributed in the Humboldt Current System.

Chile has not yet ratified the U.N. 1995 Agreement on straddling/highly migratory fish stocks. This paper discusses key economic issues at stake from the viewpoint of a coastal state with important stakes in a straddling stock. The Chilean jack mackerel stock, one of Chile's most important fish resources, is in this category. This stock is currently caught on adjacent high-seas only by a Chilean-flag fleet, and currently there is no evidence of imminent competition from distant water fishing nations (DWFNs). We argue that ratification of the Agreement could imply negative effects on: (i) coastal states ' sovereignty upon management measures within its Exclusive Economic Zone (EEZ) and (ii) national fishing companies' competitiveness. Despite this, the net cost/benefit balance depends on how binding the threat of DWFNs' fishing competition is expected to be. If the Agreement does go into force, coastal states with important stakes in straddling fish stocks will feel increased pressure to ratify as well. Fo...

Barangé, Manuel ... et al., The assessment and management of small pelagic fish (SPF) stocks is particularly difficult and uncertain because their short life expectancy, characteristic aggregative behavior, rapid response to climate and environmental signals and large and variable natural mortality make them less tractable through traditional population dynamic models and assumptions. In this review we summarize the assessment and management approaches applied in 29 SPF stocks or management units (12 anchovy, 10 sardine, 4 herring, and 3 sprat). The review demonstrates that the assessment and management of SPF varies substantially in its approach and performance between stocks and regions. Most stocks have a scientific assessment program in place and a management approach that generally takes into account assessment results, but in some stocks management practices deviate substantially from scientific advice and in some, assessment and management processes are largely disconnected. It is concluded that only properly tailored scientific assessment and management programs can provide the speed of response and the flexibility of management that highly variable SPF demand. The most effective monitoring programs are based on fishery-independent surveys (daily egg production or/and hydroacoustics), while analyses based on catch per unit effort offer limited value. Most assessments, defined as what management uses to base its decisions on, rely on catch-at-age or yield per recruit models. Harvest strategies range from those driven by harvest control rules to those derived from outputs of best assessment runs. Some stocks use operating models based on age–structure model outputs or forward VPA. On the issue of scientific uncertainty some practitioners propose reducing it through additional science and measures, while others promote the development of management procedures robust to uncertainty