Alex Aguilar

Geographical and temporal variation in levels of organochlorine contaminants in marine mammals

The interpretation of the spatial and temporal patterns of variation in organochlorine concentrations in marine mammal populations is complex because of the lack of wide-scale, long-term surveys. Therefore the results from several surveys must be combined and this causes undesired heterogeneity due to differences in the sampling and analytical techniques used and in the biological characteristics of the individuals sampled. Moreover, information is not homogeneously distributed in either space or in time. Most research is concentrated in western Europe, northern America and certain areas of Asia, while it is extremely limited or non-existent in Africa and most regions of the southern hemisphere. Marine mammals from the temperate fringe of the northern hemisphere, particularly fish-eating species which inhabit the mid-latitudes of Europe and North America, show the greatest organochlorine loads; noteworthy are the extremely high levels found in the Mediterranean Sea and certain locations on the western coasts of the United States. Concentrations in the tropical and equatorial fringe of the northern hemisphere and throughout the southern hemisphere are low or extremely low. The polar regions of both hemispheres showed the lowest concentrations of DDTs and PCBs, although levels of HCHs, chlordanes and HCB were moderate to high in the cold waters of the North Pacific. During recent decades, concentrations have tended to decrease in the regions where pollution was initially high but they have increased in regions located far from the pollution source as a consequence of atmospheric transport and redistribution. It is expected that the Arctic and, to a lesser extent, the Antarctic, will become major sinks for organochlorines in the future; this process may already be significant for some compounds such as HCB and HCHs. Effort should be devoted to both assessment of organochlorine trends in the now highly polluted populations of the temperate fringe of the northern hemisphere and to the implementation of long-term monitoring of marine mammal populations inhabiting polar regions.

Population genetic structure of North Atlantic, Mediterranean Sea and Sea of Cortez fin whales, Balaenoptera physalus (Linnaeus 1758): analysis of mitochondrial and nuclear loci

Samples were collected from 407 fin whales, Balaenoptera physalus, at four North Atlantic and one Mediterranean Sea summer feeding area as well as the Sea of Cortez in the Pacific Ocean. For each sample, the sex, the sequence of the first 288 nucleotides of the mitochondrial (mt) control region and the genotype at six microsatellite loci were determined. A significant degree of divergence was detected at all nuclear and mt loci between North Atlantic/Mediterranean Sea and the Sea of Cortez. However, the divergence time estimated from the mt sequences was substantially lower than the time elapsed since the rise of the Panama Isthmus, suggesting occasional gene flow between the North Pacific and North Atlantic ocean after the separation of the two oceans. Within the North Atlantic and Mediterranean Sea, significant levels of heterogeneity were observed in the mtDNA between the Mediterranean Sea, the eastern (Spain) and the western (the Gulf of Maine and the Gulf of St Lawrence) North Atlantic. Samples collected off West Greenland and Iceland could not be unequivocally assigned to either of the two areas. The homogeneity tests performed using the nuclear data revealed significant levels of divergence only between the Mediterranean Sea and the Gulf of St Lawrence or West Greenland. In conclusion, our results suggest the existence of several recently diverged populations in the North Atlantic and Mediterranean Sea, possibly with some limited gene flow between adjacent populations, a population structure which is consistent with earlier population models proposed by Kellogg, Ingebrigtsen, and Sergeant.

Habitat structure and the dispersal of male and female bottlenose dolphins (Tursiops truncatus)

Bottlenose dolphins (Tursiops truncatus) are widely distributed and a high degree of morphometric and genetic differentiation has been found among both allopatric and parapatric populations. We analysed 145 samples along a contiguous distributional range from the Black Sea to the eastern North Atlantic for mitochondrial and nuclear genetic diversity, and found population structure with boundaries that coincided with transitions between habitat regions. These regions can be characterized by ocean floor topography, and oceanographic features such as surface salinity, productivity and temperature. At the extremes of this range there was evidence for the directional emigration of females. Bi-parentally inherited markers did not show this directional bias in migration, suggesting a different dispersal strategy for males and females at range margins. However, comparative assessment based on mitochondrial DNA and nuclear markers indicated that neither sex showed a strong bias for greater dispersal on average. These data imply a mechanism for the evolutionary structuring of populations based on local habitat dependence for both males and females.

Emerging infectious diseases in cetaceans worldwide and the possible role of environmental stressors.

We reviewed prominent emerging infectious diseases of cetaceans, examined their potential to impact populations, re-assessed zoonotic risk and evaluated the role of environmental stressors. Cetacean morbilliviruses and papillomaviruses as well as Brucella spp. and Toxoplasma gondii are thought to interfere with population abundance by inducing high mortalities, lowering reproductive success or by synergistically increasing the virulence of other diseases. Severe cases of lobomycosis and lobomycosis-like disease (LLD) may contribute to the death of some dolphins. The zoonotic hazard of marine mammal brucellosis and toxoplasmosis may have been underestimated, attributable to frequent misdiagnoses and underreporting, particularly in developing countries and remote areas where carcass handling without protective gear and human consumption of fresh cetacean products are commonplace. Environmental factors seem to play a role in the emergence and pathogenicity of morbillivirus epidemics, lobomycosis/LLD, toxoplasmosis, poxvirus-associated tattoo skin disease and, in harbour porpoises, infectious diseases of multifactorial aetiology. Inshore and estuarine cetaceans incur higher risks than pelagic cetaceans due to habitats often severely altered by anthropogenic factors such as chemical and biological contamination, direct and indirect fisheries interactions, traumatic injuries from vessel collisions and climate change.

Isomer-specific analysis and toxic evaluation of polychlorinated biphenyls in striped dolphins affected by an epizootic in the western Mediterranean sea.

Isomer-specific concentrations of polychlorinated biphenyls (PCBs) including planar, mono- and di-ortho congeners and concentrations of DDT were determined in striped dolphins affected by a morbillivirus epizootic in the western Mediterranean in 1990. Extremely high concentrations of PCBs ranging from 94 to 670 μg/g (wet wt) were detected in the blubber. Similarly, DDT concentrations were high, between 22 and 230 μg/g (wet wt). The concentrations of three non-ortho coplanar PCBs were 43 (3,3′,4,4′-T4CB), 6.8 (3,3′,4,4′,5-P5CB), and 7.8 (3,3′,4,4′,5,5′-H6CB) ng/g (wet wt), respectively, the highest residue levels reported to date. The estimated 2,3,7,8-TCDD toxic equivalents of non-, mono- and di-ortho PCB congeners in striped dolphins were several times higher than those observed for other marine mammals and humans. Mono-ortho congeners contributed greater 2,3,7,8-TCDD toxic equivalents than non-ortho members. The higher ratio of 3,3′,4,4′,5,5′-H6CB/3,3′,4,4′,5-P5CB (IUPAC 169/126) suggested a strong induction of mixed function oxidase enzymes and highlighted the possibility of using this ratio as an index for risk assessment of PCB contamination in marine mammals. Elevated concentrations of PCBs may have played a role in the immune depression in striped dolphins, ultimately leading to the development of morbillivirus disease.

Massive Consumption of Gelatinous Plankton by Mediterranean Apex Predators

Stable isotopes of carbon and nitrogen were used to test the hypothesis that stomach content analysis has systematically overlooked the consumption of gelatinous zooplankton by pelagic mesopredators and apex predators. The results strongly supported a major role of gelatinous plankton in the diet of bluefin tuna (Thunnus thynnus), little tunny (Euthynnus alletteratus), spearfish (Tetrapturus belone) and swordfish (Xiphias gladius). Loggerhead sea turtles (Caretta caretta) in the oceanic stage and ocean sunfish (Mola mola) also primarily relied on gelatinous zooplankton. In contrast, stable isotope ratios ruled out any relevant consumption of gelatinous plankton by bluefish (Pomatomus saltatrix), blue shark (Prionace glauca), leerfish (Lichia amia), bonito (Sarda sarda), striped dolphin (Stenella caerueloalba) and loggerhead sea turtles (Caretta caretta) in the neritic stage, all of which primarily relied on fish and squid. Fin whales (Balaenoptera physalus) were confirmed as crustacean consumers. The ratios of stable isotopes in albacore (Thunnus alalunga), amberjack (Seriola dumerili), blue butterfish (Stromaeus fiatola), bullet tuna (Auxis rochei), dolphinfish (Coryphaena hyppurus), horse mackerel (Trachurus trachurus), mackerel (Scomber scombrus) and pompano (Trachinotus ovatus) were consistent with mixed diets revealed by stomach content analysis, including nekton and crustaceans, but the consumption of gelatinous plankton could not be ruled out completely. In conclusion, the jellyvorous guild in the Mediterranean integrates two specialists (ocean sunfish and loggerhead sea turtles in the oceanic stage) and several opportunists (bluefin tuna, little tunny, spearfish, swordfish and, perhaps, blue butterfish), most of them with shrinking populations due to overfishing.

Reproductive transfer and variation of body load of organochlorine pollutants with age in fin whales (Balaenoptera physalus)

The body load of tDDT (p,p′DDT + o,p′DDT + p,p′DDE+p,p′TDE) and polychlorinated biphenyls (sum of congeners) was estimated for 169 fin whales to study age and sex-related variation and to calculate the quantity of these compounds transferred to offspring through reproduction. Blubber was the body compartment containing the greatest quantities of organochlorines, but its relative contribution to total load was lower than in other cetaceans because in fin whales muscle and bone are also significant lipid reserve sites. In male fin whales, organochlorine body loads increased with age but tended to reach a plateau in fully grown individuals. In adult females, loads decreased with age because of transfer to offspring canceling the rise in loads associated with body growth; as a consequence, the amount of organochlorines transferred during a reproductive cycle also declined with age. This transfer is lower than that found for other cetaceans because fin whales have a shorter lactation period. According to the calculations, the first offspring of a female fin whale receives about 1 g of PCB and about 1.5 g of tDDT. These amounts will progressively decrease in subsequent reproductive cycles to reach a minimum of 0.2 g PCB and 0.3 g tDDT in an old female. Therefore, the first calf delivered is the one most likely to be affected by pollutants.

Patterns of Lipid Content and Stratification in the Blubber of Fin Whales (Balaenoptera physalus)

The lipid content and layering structure of the blubber of 82 fin whales ( Balaenoptera physalus ) caught off Spain were studied in relation to individual biological attributes. The lipid content of the external blubber stratum is stable and shows no apparent variation with age, reproductive status, or day of capture in either sex. This indicates that this stratum does not play a significant role in the dynamics of fat storage in fin whales. The internal stratum, in contrast, is variable, clearly reflecting the nutritive reserves of individuals. The mid-stratum is a transition between the external and internal layers. Reproductive categories are discriminated best by the mean of the values of the three layers than by any of them used independently. For this reason, this mean is proposed as the best index of condition for fin whales. Reproductive status is the main factor determining variation in lipid content of blubber in females, but is meaningless in males. Ranking of blubber fatness for the reproductive categories is: pregnant females > males = immature females > resting females > lactating females. These dissimilarities are explained by the energetic, migrational, and physiological characteristics of the different population components. In males, lipid content of blubber decreased significantly with age, whereas in immature females it increased with age. In both sexes, lipid reserves accrued from early May until mid-August, but tended to decrease afterwards, following variations in food availability. The nutritive condition of lactating females improved during late lactation probably because of increasing food consumption and decreasing energetic demands of suckling young.

Compartmentation and reliability of sampling procedures in organochlorine pollution surveys of cetaceans

The study of the effects of chemical pollution on wildlife basically straddles three scientific disciplines: chemistry, ecology and zoology. The research chemist must elaborate systems for detecting and precise quantifying of the different compounds found in the tissues of living organisms, and must study those properties of such compounds which explain the basic processes of transfer and accumulation in the ecosystem. The ecologist must put this data together with his own knowledge of the dynamic processes which regulates the ecosystem, both on a general level (movements of air and water masses), and on a particular one (trophic chains, migrations, etc.). Finally, the zoologist must bring his knowledge to bear on the biology of the species which are to be studied, in order that the results maybe correctly evaluated and not biased by the particular characteristics of the animals sampled (physiological or reproductive state, age, etc.).

Spanish driftnet fishing and incidental catches in the western Mediterranean

Abstract The Spanish driftnet fishery operating since 1994 on the Mediterranean side of the Gibraltar Straits was an illegal activity whose main target was the swordfish Xiphias gladius but which also caught other species incidentally, particularly sunfish Mola mola. Observations during the 1993 and 1994 seasons showed that the fleet was composed of 27 boats deploying nets 3–4 km long. Swordfish constituted 7% of the catch in 1992, 5% in 1993 and 7% in 1994. Sunfish represented 71% of the catch in 1992, 93% in 1993 and 90% in 1994. Sea turtles, mainly loggerhead turtles Caretta caretta, constituted 0.32% of the total catch in 1993 and 0.92% in 1994. The incidental capture of small cetaceans, composed entirely of common dolphins Delphinus delphis in 1992 and of striped dolphin Stenella coeruleoalba and common dolphins in roughtly equal proportions in 1993 and 1994, constituted 0.9% of the catch in 1992, 0.6% in 1993 and 1% in 1994. The bycatch rate of dolphins was 0.1 individuals per km of net set. The total catch of dolphins can therefore be estimated at 366 (95% confidence interval 268–464) animals for the 1993 fishing season and 289 (CI 238–340) for that of 1994. If these figures are added to the undetermined catches of dolphins by the Italian and Moroccan driftnet fleets also operating in the region, it is possible that these catches are not sustainable. ©