Alejo J. Irigoyen

Global conservation outcomes depend on marine protected areas with five key features

In line with global targets agreed under the Convention on Biological Diversity, the number of marine protected areas (MPAs) is increasing rapidly, yet socio-economic benefits generated by MPAs remain difficult to predict and under debate. MPAs often fail to reach their full potential as a consequence of factors such as illegal harvesting, regulations that legally allow detrimental harvesting, or emigration of animals outside boundaries because of continuous habitat or inadequate size of reserve. Here we show that the conservation benefits of 87 MPAs investigated worldwide increase exponentially with the accumulation of five key features: no take, well enforced, old (>10 years), large (>100 km2), and isolated by deep water or sand. Using effective MPAs with four or five key features as an unfished standard, comparisons of underwater survey data from effective MPAs with predictions based on survey data from fished coasts indicate that total fish biomass has declined about two-thirds from historical baselines as a result of fishing. Effective MPAs also had twice as many large (>250 mm total length) fish species per transect, five times more large fish biomass, and fourteen times more shark biomass than fished areas. Most (59%) of the MPAs studied had only one or two key features and were not ecologically distinguishable from fished sites. Our results show that global conservation targets based on area alone will not optimize protection of marine biodiversity. More emphasis is needed on better MPA design, durable management and compliance to ensure that MPAs achieve their desired conservation value.

Effects of the alien algae Undaria pinnatifida (Phaeophyceae, Laminariales) on the diversity and abundance of benthic macrofauna in Golfo Nuevo (Patagonia, Argentina): potential implications for local food webs

Changes in macroalgal community structure caused by invasive seaweeds have strong impacts on the associated macrofauna due to the role of macroalgae as autogenic ecosystem engineers. This study investigates the effect of Undaria pinnatifida on the abundance and diversity of benthic macrofauna in Golfo Nuevo, northern Patagonia, using a manipulative experiment involving the systematic removal of Undaria microthalli from strips of hard bottom during its eighth-month growing period. Species richness and diversity were higher in plots covered by Undaria than when Undaria was removed. Also, the abundance of two species of crustaceans, one species of sea urchin, one species of nemertina and several species of polychaetes was higher. We attribute these effects to the provision of new habitat structure by Undaria, a larger and structurally more complex species than the local native seaweeds. These results support the hypothesis that complex habitats enhance abundance and species richness, by offering different shelter and foraging opportunities compared to morphologically simpler habitats. Based on a review of diet studies in the region, we speculate that Undaria could potentially produce a bottom-up effect on local food chains by increasing abundance of prey for a wide variety of predators, from invertebrates to marine mammals. While our study has a narrow temporal and spatial scale, we expect similar effects of Undaria on the macrofauna in other sites of the Argentine coast, especially those dominated by small native macroalgae.

The Reef-fish Fauna of the Northern Patagonian Gulfs, Argentina, South- western Atlantic

A checklist containing 29 species of reef fishes recorded at the gulfs San Jose and Nuevo in Argentina (~42o- 43oS) is provided. The reef-fish assemblages of the San Jose and Nuevo gulfs are a mix of warm-temperate fauna from the South-western Atlantic Province, and cold-temperate species from the South-American Province; however, warm- temperate fishes dominated in both gulfs. The presence of the families Bovichtidae, Eleginopidae, Nototheniidae, Congiopodidae, Sebastidae and Moridae distinguished the Patagonian region from the rest of the Atlantic coast.

Variability in Abundance of Temperate Reef Fishes Estimated by Visual Census

Identifying sources of sampling variation and quantifying their magnitude is critical to the interpretation of ecological field data. Yet, most monitoring programs of reef fish populations based on underwater visual censuses (UVC) consider only a few of the factors that may influence fish counts, such as the diver or census methodology. Recent studies, however, have drawn attention to a broader range of processes that introduce variability at different temporal scales. This study analyzes the magnitude of different sources of variation in UVCs of temperate reef fishes off Patagonia (Argentina). The variability associated with time-of-day, tidal state, and time elapsed between censuses (minutes, days, weeks and months) was quantified for censuses conducted on the five most conspicuous and common species: Pinguipes brasilianus, Pseudopercis semifasciata, Sebastes oculatus, Acanthistius patachonicus and Nemadactylus bergi. Variance components corresponding to spatial heterogeneity and to the different temporal scales were estimated using nested random models. The levels of variability estimated for the different species were related to their life history attributes and behavior. Neither time-of-day nor tidal state had a significant effect on counts, except for the influence of tide on P. brasilianus. Spatial heterogeneity was the dominant source of variance in all but one species. Among the temporal scales, the intra-annual variation was the highest component for most species due to marked seasonal fluctuations in abundance, followed by the weekly and the instantaneous variation; the daily component was not significant. The variability between censuses conducted at different tidal levels and time-of-day was similar in magnitude to the instantaneous variation, reinforcing the conclusion that stochastic variation at very short time scales is non-negligible and should be taken into account in the design of monitoring programs and experiments. The present study provides baseline information to design and interpret results from visual census programs in temperate reefs.

Depletion of trophy large-sized sharks populations of the Argentinean coast, south-western Atlantic: insights from fishers' knowledge

Globally, sharks are impacted by a wide range of human activities, resulting in many populations being depleted. Trophy large-sized sharks of the Argentinean coast, the sand-tiger Carcharias taurus , the copper Carcharhinus brachyurus and the sevengill shark Notorynchus cepedianus are under intense sport and artisanal fishing since the 50s decade. However, the current and historical information for the assessment of its populations status is scarce. The aim of this work was to analyze the status of conservation of these species through the gathering of expert fishermen knowledge (FK) on semi-structured interviews. Abundance variation perception between the beginning and the end of fishermen careers revealed a critical status for the species study (means variation between -77 and -90 %). Furthermore, a best days catch analysis reinforce this result in the case of the sand tiger shark. The school shark Galeorhinus galeus was included on this work with the objective of contrast FK with formal information available of catch-per-unit-effort (CPUE) time series. Both sources of information, despite are not comparable, shows declines ~ - 80%. The critical conservation situation of study species needs urgent management action, particularly for the san tiger shark which could became regionally extinct before the reaction of stakeholders occurs.

Spatial dynamics of the Argentine sandperch, Pseudopercis semifasciata (Pinguipedidae), in temperate rocky reefs from northern Patagonia, Argentina

The choice of appropriate conservation strategies for reef fishes depends on their mobility, degree of site fidelity and residence times. Here we report the results of a small-scale mark–recapture and resighting study conducted to investigate the spatial dynamics of the Argentine sandperch, Pseudopercis semifasciata. This is the flagship species of the rocky-reef fish assemblage from northern Patagonia, which has been the target of uncontrolled fishing since the early 1950s. About 19% of the fish tagged were recaptured up to four years after tagging. In total, 180 of 218 recaptured fish stayed in the reef of tagging. Thirty-six of 57 recaptures made at known locations within popular fishing areas of San Jose Gulf, densely covered by patchy reefs, occurred within 100 m of the tagging site, up to 793 days after tagging. Six fish were recovered more than 1 km from where they were tagged. Smaller fish were more prone to relocate, and were recovered farther from the tagging site. Fish stayed in the reefs for periods longer than a year; larger males remained longer in the same reefs. Our results indicate that relatively small reserves (in the order of a few kilometres) could be effective at protecting P. semifasciata populations within the northern Patagonian gulfs.

Estimating tissue‐specific discrimination factors and turnover rates of stable isotopes of nitrogen and carbon in the smallnose fanskate Sympterygia bonapartii (Rajidae)

This study aimed to estimate trophic discrimination factors (TDFs) and metabolic turnover rates of nitrogen and carbon stable isotopes in blood and muscle of the smallnose fanskate Sympterygia bonapartii by feeding six adult individuals, maintained in captivity, with a constant diet for 365 days. TDFs were estimated as the difference between δ(13) C or δ(15) N values of the food and the tissues of S. bonapartii after they had reached equilibrium with their diet. The duration of the experiment was enough to reach the equilibrium condition in blood for both elements (estimated time to reach 95% of turnover: C t95%blood  = 150 days, N t95%blood  = 290 days), whilst turnover rates could not be estimated for muscle because of variation among samples. Estimates of Δ(13) C and Δ(15) N values in blood and muscle using all individuals were Δ(13) Cblood = 1·7‰, Δ(13) Cmuscle = 1·3‰, Δ(15) Nblood = 2·5‰ and Δ(15) Nmuscle = 1·5‰, but there was evidence of differences of c.0·4‰ in the Δ(13) C values between sexes. The present values for TDFs and turnover rates constitute the first evidence for dietary switching in batoids based on long-term controlled feeding experiments. Overall, the results showed that S. bonapartii has relatively low turnover rates and isotopic measurements would not track seasonal movements adequately. The estimated Δ(13) C values in S. bonapartii blood and muscle were similar to previous estimations for elasmobranchs and to generally accepted values in bony fishes (Δ(13) C = 1·5‰). For Δ(15) N, the results were similar to published reports for blood but smaller than reports for muscle and notably smaller than the typical values used to estimate trophic position (Δ(15) N c. 3·4‰). Thus, trophic position estimations for elasmobranchs based on typical Δ(15) N values could lead to underestimates of actual trophic positions. Finally, the evidence of differences in TDFs between sexes reveals a need for more targeted research.

The reproductive biology of Pinguipes brasilianus Cuvier, 1829 (Osteichthyes: Pinguipedidae) in temperate rocky reefs of Argentina

Pinguipes brasilianus is a conspicuous and abundant rocky-reef fish inhabiting the Northern Patagonian gulfs of Argentina, Southwest Atlantic. This study describes its reproductive biology in this region. We made macroscopic and histological descriptions of the testis and ovary development, analyzed the evolution of the gonadosomatic index (GSI) in both sexes throughout the year, and estimated fecundity and length at 50% maturity for females. Pinguipes brasilianus is a multiple spawner with indeterminate annual fecundity and an extended reproductive season, encompassing austral spring and summer. Low GSI values in males (monthly means ranged between 0.11% and 0.75%) and low relative fecundity in female fish (between 2 and 44 oocytes/g) are consistent with a need of close proximity between male and female during oocyte fertilization, sexual courtship and with spawning in pairs and/or within reef crevices. The estimated length at 50% maturity (± SD) for females was 15.22 ± 0.43 cm total length. Although P. brasilianus shares the main reproductive features of its congeneric species Pinguipes chilensis , male GSI and female length at 50% maturity in P. brasilianus were markedly lower than those reported for P. chilensis , while relative and batch fecundity were greater in fish of the same size.

The "Tracked Roaming Transect" and distance sampling methods increase the efficiency of underwater visual censuses

Underwater visual census (UVC) is the most common approach for estimating diversity, abundance and size of reef fishes in shallow and clear waters. Abundance estimation through UVC is particularly problematic in species occurring at low densities and/or highly aggregated because of their high variability at both spatial and temporal scales. The statistical power of experiments involving UVC techniques may be increased by augmenting the number of replicates or the area surveyed. In this work we present and test the efficiency of an UVC method based on diver towed GPS, the Tracked Roaming Transect (TRT), designed to maximize transect length (and thus the surveyed area) with respect to diving time invested in monitoring, as compared to Conventional Strip Transects (CST). Additionally, we analyze the effect of increasing transect width and length on the precision of density estimates by comparing TRT vs. CST methods using different fixed widths of 6 and 20 m (FW3 and FW10, respectively) and the Distance Sampling (DS) method, in which perpendicular distance of each fish or group of fishes to the transect line is estimated by divers up to 20 m from the transect line. The TRT was 74% more time and cost efficient than the CST (all transect widths considered together) and, for a given time, the use of TRT and/or increasing the transect width increased the precision of density estimates. In addition, since with the DS method distances of fishes to the transect line have to be estimated, and not measured directly as in terrestrial environments, errors in estimations of perpendicular distances can seriously affect DS density estimations. To assess the occurrence of distance estimation errors and their dependence on the observer’s experience, a field experiment using wooden fish models was performed. We tested the precision and accuracy of density estimators based on fixed widths and the DS method. The accuracy of the estimates was measured comparing the actual total abundance with those estimated by divers using FW3, FW10, and DS estimators. Density estimates differed by 13% (range 0.1–31%) from the actual values (average = 13.09%; median = 14.16%). Based on our results we encourage the use of the Tracked Roaming Transect with Distance Sampling (TRT+DS) method for improving density estimates of species occurring at low densities and/or highly aggregated, as well as for exploratory rapid-assessment surveys in which divers could gather spatial ecological and ecosystem information on large areas during UVC.

Seasonality of immunological and health-state parameters of wild broadnose sevengill shark, Notorynchus cepedianus.

Seasonal fluctuation in environmental parameters can influence immune responses of vertebrates and consequently influence their health and disease resistance. Although seasonality of immune function is well documented in a broad range of vertebrate taxa, this information remains virtually unexplored in cartilaginous fish. Here we examine seasonal variation in immune and general-health parameters of free-living adult broadnose sevengill sharks, Notorynchus cepedianus, along an annual cycle. We sampled sharks during autumn/winter (i.e., coolest temperatures and nonreproductive period) and spring/summer (i.e., warmest temperatures and active reproductive period) and assessed aspects of immunity, general condition, and reproductive hormone levels. A seasonal influence was observed in some, but not all, parameters evaluated. Lower lymphocyte counts and higher heterophil counts and granulocyte to lymphocyte (G∶L) ratios were observed in sharks sampled during autumn/winter than in those sampled during spring/summer. On the other hand, total leukocyte counts, eosinophil counts, bacterial agglutination mediated by natural antibodies, and hematocrit did not vary seasonally. The observed seasonal patterns could be explained as (1) greater levels of stress based on the G∶L ratio, (2) a sign of immunosuppression or depressed immune investment based on the low lymphocyte counts, and/or (3) a sign of ongoing infection based on the higher heterophil counts in the colder seasons with respect to the warmer ones. In addition, the pattern is in line with the notion that while acquired components are usually depressed by lower temperatures, some innate components might increase to offset that reduction. Immune and health-state parameters were mostly independent of reproductive hormone levels, providing little support for a trade-off with reproduction. Overall, the observed seasonal pattern in immunity of broadnose sevengill sharks could be related to changes in abiotic environmental condition, such as water temperature and photoperiod, although other factors such as availability of high-quality food may play a part.