Sandra L. Marín

Is there a possibility of ranking benthic quality assessment indices to select the most responsive to different human pressures

Although a plethora of benthic indices exist, there is no agreement on what index or indices should be used by environmental managers to establish benthic quality. The objective of this investigation was to rank 35 benthic quality assessment indices used in different countries to evaluate the impact produced by 15 different human pressures (including multipressure, aquaculture, sewage discharges, eutrophication, physical alteration, chemical pollution, climate change, etc.). The ranking was determined by taking into account the coverage area of biogeographical provinces, number of citations testing a pressure and number of citations with significant correlation with pressure. We analysed 363 references, of which 169 showed quantitative data. Over a potential total score of 100, the highest values were obtained by the following indices: (i) AZTIs Marine Biotic Index (AMBI), which scored 77, tested by using 14 pressures in 14 provinces from the Arctic to tropical seas; (ii) multivariate AMBI (M-AMBI), which scored 74, tested with 12 pressures in 13 provinces; (iii) Bentix (BENTIX), which scored 68, tested with nine pressures in six provinces; (iv) Benthic Quality Index (BQI), which scored 66, tested with five pressures in seven provinces; and (v) Benthic Opportunistic Polychaetes Amphipods (BOPA) index, which scored 62, tested with eight pressures in six provinces.

Simulation of alternative management strategies for red algae, luga roja, (Gigartina skottsbergii Setchell and Gardner) in southern Chile

The objective of this study was to examine the response of a Gigartina skottsbergii population, a commercial red algal species from southern Chile, to different management strategies using a simulation model. The impact of present harvesting techniques, varying the recommended size at harvest and the rate of harvest were evaluated. Model development followed Grant et al. (Ecology and Natural Resource Management: Systems Analysis and Simulation. Wiley, New York, 1997) and the data base was obtained from available literature. The model simulates population dynamics of G. skottsbergii and in terms of both number of fronds and biomass per size class. Model predicts an annual pattern of variation for biomass determined by variations in seasonal factors. However, biomass has a 2 year cycle of alternate years with high biomass and low biomass. This production cycle can be attributed to changes in population size structure and density, and to the existence of discrete recruitment events. Results predicted from using different management strategies suggest that commercial harvest should be based on selection for larger fronds and restricted harvest period. Under this scenario harvest rate can be relaxed since no important changes in harvest biomass were predicted when increasing harvest rate from 50 to 90%, at least in the short term. However, it is recommendable to keep it low (50%) as a preventive mechanism, since results suggest that in the long term, a harvest rate of 50% could produce larger harvested biomass. The existence of a biennial cycle of biomass production suggests that populations should be harvested in rotation. Several aspects of the model must be improved in order to obtain better prediction of both specific values as well as dynamics. These include winter recruitment, frond breakage, longevity of larger sized fronds, and a more complete analysis of changes in the size structure of the population.

The feasibility of using Udonella sp. (Platyhelminthes: Udonellidae) as a biological control for the sea louse Caligus rogercresseyi, Boxshall and Bravo 2000, (Copepoda: Caligidae) in southern Chile

Caligus rogercresseyi is a sea louse of native and farmed fish in southern Chile. Due to the impact that this copepod has on the Chilean salmonid production, it is necessary to search for control mechanisms that can effectively reduce its population. This study focuses on determining the feasibility of using Udonella sp., a common flatworm found on copepod ectoparasites of the Chilean rock cod, Eleginops maclovinus, as a biological control for sea lice. The following aspects were studied: distribution and preference of Udonella sp. regarding both host sex and body location on copepods collected from both the Chilean rock cod and cultured salmonids; the effect of Udonella on both fecundity and survival of the free-living stages; and seasonal variations of population of both Udonella and the copepod. Results indicated that Udonella sp. is frequently found on copepods collected from the Chilean rock cod, but is absent on those from cultured salmonids. The flatworm showed a marked preference for female copepods and the main body locations used by Udonella are the genital complex and egg sacs. The three life stages of Udonella are distributed across the copepod body in different ways since different body locations represent feeding and nursery areas. Udonella has no significant effect either on fecundity or survival of free-living stages. Udonella may maintain its population relatively independent of the Caligus infra-population all year round. Seasonal patterns of variation were not evident for the population parameters of either Caligus or Udonella, probably due to the exceptional environmental conditions that occurred during 1997 that allowed Caligus populations to remain high during fall and winter, instead of decreasing as it has been reported previously. Results suggest that Udonella cannot be used as a biological control for sea lice since it is not found naturally on salmonid species and because the presence of Udonella did not reduce either fecundity or survival of free-living stages of copepods.

A NEW GENUS OF DACTYLOGYRID FROM THE GILLS OF GALAXIAS MACULATUS (OSMERIFORMES: GALAXIIDAE) IN MAULLIN BASIN, PATAGONIA, CHILE

During a parasitological survey of Galaxias maculatus (Jenyns, 1842) in the Maullín Basin (Chilean Patagonia), specimens of a new species of Monogenea were collected from the gills. This species is described as the only member of a proposed new genus, Inserotrema n. gen. (Dactylogyridae, Ancyrocephalinae), characterized by similar hooks with 2 subunits, overlapping gonads, coiled cirrus with counterclockwise rings, articulated accessory piece formed by 2 parts, a needlelike sclerite threading the distal part of the MCO, and a sclerotized midventral vagina. This new genus is proposed for dactylogyrids from gills of galaxiids (Galaxiidae). Inserotrema puyei n. sp. infects gills of G. maculatus from Llanquihue Lake, Maullín River, and Maullín Estuary. This is the first species of Ancyrocephalinae described from gills of a galaxiid.

Dispersal of Udonella australis (Monogenea: Udonellidae) between caligid copepods Caligus rogercresseyi and Lepeophtheirus mugiloidis on Chilean rock cod.

Udonella australis is a platyhelminth that lives on the surface of the ectoparasite copepods Caligus rogercresseyi and Lepeophtheirus mugiloidis, which coexist on the Chilean rock cod Eleginops maclovinus. The absence of a planktonic oncomiracidium stage in the life cycle of udonellids may limit their dispersal ability. However, the high prevalence and intensity of U. australis on C. rogercresseyi suggest they have developed dispersal strategies to compensate for the lack of a free-living larval stage. The goals of this study were to determine the main dispersal mechanisms of U. australis in 1 copepod species and to compare the dispersal ability of U. australis between 2 different copepod species. Chilean rock cods were infected with female (without udonellids) and male (with and without udonellids) C. rogercresseyi. Other fishes were also infected with this copepod (with U. australis) and with L. mugiloidis (without U. australis). The dispersal of udonellids among copepods occurs through both intraspecific and interspecific processes. The main dispersal mechanism appears to be copepod mating; contact between same-sex individuals is less important. Intraspecific dispersal seems to be more dependent on the number of udonellids per fish than on copepod abundance, as observed for interspecific dispersal.

Response of Caligus rogercresseyi (Boxshall & Bravo, 2000) to treatment with Hydrogen Peroxide: Recovery of parasites, fish infestation and egg viability under experimental conditions

Hydrogen peroxide (HP) is used to remove C. rogercresseyi from fish but little is known about its effect on this species. This study determined EC50 and concentration immobilizing 100% of specimens, capacity of parasites exposed to HP to recover and infest fish, and effect on survival into the copepodid stage. EC50 and concentration immobilizing 100% of specimens were estimated by exposing parasites for 20 min to 11 concentrations and evaluating effect at 1 and 24 h post-exposure. Capacity to recover and infest fish, and survival into copepodid were evaluated by exposing parasites and eggs to HP for 20 min. Recovery and fish infestation were evaluated at 25 and 24 h post-exposure, respectively. Eggs were grown until control reached the copepodid stage and survival calculated. EC50 was 709.8 ppm.100% immobilization was obtained at 825 ppm. Male and female recover 0.5 and 1 h post-exposure, respectively. Percentage of parasites exposed and not exposed to HP that were recovered on fish was not significantly different. Survival to copepodid was lower in those exposed to HP. HP effect is greater on copepodids, but 100% of the mobile stages are immobilized under 825 ppm causing detachment from fish and potentially driven away, reducing infestation risk.