Alfredo López

Fishery by-catches of marine mammals in Galician waters: results from on-board observations and an interview survey of fishermen

Rates of cetacean by-catch were investigated in Galician waters (NW Spain) using a combination of observer trips on fishing vessels, a carcase recovery scheme and an interview survey of fishermen, carried out over two years (1998–1999). All these data sources are suspected of underestimating by-catch due to the sample of co-operating fishermen being, necessarily, self-selecting. No by-catches were seen during observer trips, although not all sectors of the fishery could be covered. The carcass recovery scheme yielded seventeen cetacean carcases over two years, which compares to around 35 by-caught cetaceans recorded annually by the Galician strandings network. Analysis of interview data suggested that around 200 cetaceans might be caught annually in inshore waters and around 1500 in offshore waters. Confidence limits were wide for all estimates. The highest by-catch rates were estimated for gillnets and offshore trawling. The majority of by-catches are small dolphins, probably mainly Delphinus delphis. Smaller numbers of Tursiops truncatus and Globicephala melas are also reported. Comparing the interview estimates of by-catch rates with minimum estimates of population size, it is suggested that by-catches of D. delphis and T. truncatus may be unsustainably high and that routine monitoring of fishery by-catches in Galician fisheries is required. # 2003 Elsevier Science Ltd. All rights reserved.

Feeding ecology of Cuvier's beaked whale (Ziphius cavirostris): A review with new information on the diet of this species

Published information on the diet of Cuviers beaked whales Ziphius cavirostris (Odontoceti: Ziphiidae) is reviewed and new information on the stomach contents of three animals: two stranded in Galicia (north-west Spain) in February 1990 at A Lanzada, and in February 1995 at Portonovo; and the third stranded in February 1999 in North Uist (Scotland), is presented. The whale stranded in 1990 was a male; the other two were adult females, All animals were > 5 m long. The limited published information on the diet of this species indicates that it feeds primarily on oceanic cephalopods although some authors also found remains of oceanic fish and crustaceans. Food remains from the three new samples consisted entirely of cephalopod beaks. The Scottish sample set is the largest recorded to date for this species. The prey identified consisted of oceanic cephalopods, mainly squid (Cephalopoda: Teuthoidea). The most frequently occurring species were the squid Teuthowenia megalops, Mastigoteuthis schmidti and Taonius pavo (for the Galician whale stranded in 1990), Teuthowenia megalops and Histioteuthis reversa (for the second Galician whale) and T. megalops, Gonatus sp. and Taonius pavo (for the Scottish whale). Other prey included the squid Histioteuthis bonnellii, Histioteuthis arcturi and Todarodes sagittatus as well as Vampiroteuthis infernalis (Cephalopoda: Vampyromorpha), Stauroteuthis syrtensis and Japetella diaphana (Cephalopoda: Octopoda). The squid eaten (estimated from the measurement of the lower beaks) included juvenile and mature individuals of the most important species (Teuthowenia megalops, Gonatus sp.). The range of species found in the diet of Z. cavirostris is greater than that reported for sperm whales and bottlenosed whales in the north-east Atlantic.

Diets of marine mammals stranded on the northwestern Spanish Atlantic coast with special reference to Cephalopoda

Abstract Stomach contents from 59 marine mammals, 28 Delphinus delphis , 14 Tursiops truncatus , three Grampus griseus , four Stenella coeruleoalba , three Globicephala melas , one Ziphius cavirostris , four Phocoena phocoena , one Physeter macrocephalus and one Balaenoptera acutorostrata stranded on the northwestern Spanish Atlantic coast from December 1990 to March 1993 were examined. A total of 9076 fish otoliths and 654 cephalopod upper and lower beaks were collected. The otoliths were identified only to family level, representing by number 65% Gadidae, 24% Gobiidae, 6% Atherinidae, 2% Ammodytidae, 1.5% Clupeidae and the rest Carangidae, Labridae, Argentinidae, Macroramphosidae and Bothidae. The cephalopod beaks belonged to 12 species of nine families. The cephalopod families contributing food of these marine mammals, in order of contribution by number of specimens are, the Loliginidae (56.9%), the Octopodidae (25.3%), the Ommastrephidae (11.9%), the Sepiolidae (2.4%), the Histioteuthidae (0.9%), the Chiroteuthidae (0.9%), the Cranchiidae (0.8%), the Mastigoteuthidae (0.3%) and the Gonatidae (0.15%). The great part of the cephalopods observed in the stomach contents were small in size, except for some octopods in Grampus griseus and Globicephala melas , and Mastigoteuthis sp. in Physeter macrocephalus . The results indicated that D. delphis, T. truncatus and Phocoena phocoena are primarily fish-eating, while Grampus griseus, Globicephala melas and Physeter macrocephalus had only cephalopod remains in their stomachs.

Variability in the diet of bottlenose dolphin, Tursiops truncatus , in Galician waters, north-western Spain, 1990–2005

We describe the diet of bottlenose dolphins Tursiops truncatus in Galician waters, north-western Spain, based on 82 non-empty stomachs recovered and analysed from stranded animals between 1990 and 2005, quantifying interannual and seasonal variation in the diet, as well as dietary variation related to sex and size. The most important prey species (in terms of numerical importance and biomass) were blue whiting (Micromesistius poutassou) and hake (Merluccius merluccius), both of high commercial importance in Galician waters. Most blue whiting eaten by dolphins were mature fish but the estimated total consumption was relatively low (around 10%) compared to Spanish fishery landings of this species. In contrast, most hake eaten by dolphins were probably immature but the estimated total consumption is more than 20% of current annual fishery landings. The diet of by-caught animals, which made up around one third of the sample, was very similar to that in the overall sample. Although bottlenose dolphins are often seen close inshore, evidence from the diet suggests that they feed at the shelf edge. Evidence was found of ontogenetic dietary shifts and differences between diets of male and female dolphins. There were also clear changes in average diet over the 16-year study period, although there was no evidence that they were in response to changes in fish abundance. The amount of hake in the diet remained stable against a background of falling local abundance while the amount of blue whiting declined despite an increase in spawning stock size.

Trends in cetacean sightings along the Galician coast, north-west Spain, 2003–2007, and inferences about cetacean habitat preferences

Since mid-2003, systematic monthly sightings surveys for cetaceans have been carried out in Galicia (north-west Spain) from observation points around the coastline, with the aim of providing baseline data on cetacean distribution and habitat use to underpin future conservation measures. Here we summarize results for September 2003 to October 2007. The most frequently recorded species were the bottlenose dolphin (Tursiops truncatus, seen during 10 . 7% of observation periods), common dolphin (Delphinus delphis, 3 . 7 %), harbour porpoise (Phocoena phocoena, 1 .6%), Rissos dolphin (Grampus griseus, 0.4%) and short-finned pilot whale (Globicephala melas, 0.2%). The three most common species showed different distribution patterns along the coast. In terms of habitat preferences, bottlenose dolphins were seen to be associated with more productive areas (areas with higher chlorophyll-a concentrations) where the continental shelf was wider while both common dolphins and harbour porpoises were seen most frequently in less productive areas where the continental shelf is narrowest. Possible reasons for differences in habitat use include differing diets. In Galician waters, all three main cetacean species feed primarily on fish that are common in shelf waters, and in the case of blue whiting (the most important species in the stomach contents of common and bottlenose dolphins) abundant also on the slope. All three cetaceans feed on blue whiting while scad is important in diets of common dalphin and porpoise. It is also possible that porpoises do not use areas frequented by bottlenose dolphins in order to avoid aggressive interactions. Retrospective evaluation of the sampling regime, using data from the 2500 observation periods during 2003-2007 suggests that the overall sightings rates for all species (taking into account observation time and between-site travel time) would be higher if average observation duration was increased to at least 40 minutes. On the other hand, confidence limits on sightings rates stabilized after around 1000 observation periods, suggesting that the number of sites visited or the frequency of visits could be substantially reduced.

Trends in strandings and by-catch of marine mammals in north-west Spain during the 1990s

Strandings of marine mammals on the north-western Spanish coast (Galicia) have been systematically recorded since 1990. A total of 1433 marine mammals belonging to 15 species was recorded from 1990 to 1999. The most frequently recorded species stranded were common dolphin (47%), bottlenose dolphin (11%) and harbour porpoise (7%). The number of strandings recorded increased annually over the study period, probably reflecting an increased observer effort. During 1996–1999, an average of 1·65 animals were stranded annually for each 10 km of coastline, the highest density of strandings recorded on the Atlantic coast of the Iberian Peninsula. More than 80% of the strandings were located on the western coast of Galicia, mainly in autumn and winter. During the study period, 42 proven incidental catches were recorded, although signs of by-catch were seen in a further 198 animals. The average size of stranded common dolphins and the proportion of males both increased towards the end of the calendar year.

Results of a short study of interactions of cetaceans and longline fisheries in Atlantic waters: environmental correlates of catches and depredation events

In the Atlantic, economic losses have been reported from shark, swordfish and tuna longline fisheries due to depredation by cetaceans. We examined interactions of odontocete cetaceans with commercial longliners operating in waters off Brazil and the Azores archipelago during 2006–2007, analysing relationships between catches, depredation on hooked fish, cetacean sightings, acoustic records of cetacean presence and environmental variables. Data were provided by skippers of six vessels and by on-board observers for two vessels. The percentage of longline sets depredated by cetaceans was low (ranging from 1% to 9% of total sets per ship) but the proportion of fish damaged was high (up to 100%) when depredation occurred. Catches were related to the phase of the moon, cloud cover, sea surface temperature and water depth whereas cetacean sightings were primarily related to catches. In particular there was a positive association between Delphinus delphis sightings and catches of swordfish, and between Stenella frontalis sightings and mako catches. Acoustic detection was low when depredation by false killer whales occurred although high rates of clicks were detected when delphinids were sighted and false killer whales were by-caught. This may indicate that false killer whales are not echolocating when feeding on fish hooked on a longline.

Squid as trophic bridges for parasite flow within marine ecosystems: the case of Anisakis simplex (Nematoda: Anisakidae), or when the wrong way can be right

Long-term (1991–1997) information on parasitic infection by anisakid nematodes in cephalopods and top predators (marine mammals) of the south-eastern area of the North Atlantic underlines the important role of small cetaceans as final hosts for A. simplex. The ommastrephid squid Illex couidetii, Todaropsis eblanae and Todarodes sagittatus are the most important cephalopod paratenic hosts in the life cycle of the parasite. Information on parasite flow and parasite-caused diseases could be of use for stock assessment purposes. Moreover, it largely agrees with what is known about interactions between prey (squid) and predator (cetacean) in the same area. Parasitic castration and stomach wall ulceration were the most important parasite-caused effects recorded in infected cephalopods and cetaceans respectively.

An assessment of contaminant concentrations in toothed whale species of the NW Iberian Peninsula: Part II. Trace element concentrations

Concentrations of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn were investigated in the liver and kidney of the five most common toothed whales off the Northwest Iberian Peninsula (NWIP), specifically common dolphin, long-finned pilot whale, harbour porpoise, striped dolphin and bottlenose dolphin. Differences were observed in the bioaccumulation of the above elements between the five species. The differences are probably related to biological factors such as age and sex and/or to ecological factors specific to each species such as feeding habits or bioavailability of the various elements. However, no significant relationship was observed between element accumulation and sex. Pilot whale and striped dolphin showed the highest concentrations of renal Cd and the highest concentrations of hepatic Hg and Se, while bottlenose dolphin showed the highest concentrations of Hg in kidneys. An analysis of inter-elemental relationships showed strong positive correlations between Hg and Se in the five species, however most individuals have Hg:Se molar ratio less than 1:1 indicating an excess of Se compare to Hg. This result, probably reflect the high proportion of young animals in the sample available for this study and/or that these animals had a good health status. We also observed a positive correlation in striped dolphins between Cd and Cu and between Cd and Zn in kidneys. In addition, comparing with other studies world-wide, the element concentrations (Hg and Cd) found in Iberian toothed whales indicate that these populations are not specially threatened by Hg and Cd exposure in the area.

Dentinal anomalies in teeth of harbour porpoises (Phocoena phocoena) from Scottish waters: are they linked to sexual maturation and environmental events?

We examined the tooth ultra-structure of harbour porpoises ( Phocoena phocoena ) from Scottish waters to determine whether the incidence of mineralization anomalies could be related to certain life history events (e.g. the achievement of sexual maturation) as well as other factors that affect the general health of the individual (e.g. persistent organic pollutant (POP) concentrations in blubber). Five distinct types of mineralization anomalies were recorded: accessory lines, marker lines, dentinal resorption, cemental disturbance and pulp stones and the occurrence of these anomalies was scored by sex, age and maturity state. Overall, the incidence of mineralization anomalies was high and tended to increase with age. Marker lines and accessory lines were the most commonly recorded anomalies while pulp stones were least frequent. Duplicate teeth (i.e. from the same individual) always showed the same pattern of anomaly occurrence. Fitted binary generalized linear and additive models indicated that the presence of dentinal resorption, cemental disturbance and marker lines in harbour porpoise teeth increased with age, body length and maturity. Males displayed marker lines more frequently than females. Age was the best predictor of the incidence of dentinal resorption and cemental disturbance while age and sex were the best predictors of the incidence of marker lines. The time course of appearance of dentinal resorption and cemental disturbance suggests that their occurrence could be related to physiological stress linked to sexual maturation. Marker lines were found within growth layer groups which coincided with the beginning of weaning and sexual maturation, suggesting an association with these two major life history events. Accessory lines were found in most teeth and may be a normal characteristic of porpoise teeth or reflect regular events. Pulp stones appeared only in mature animals. We found no evidence that the presence of anomalies in teeth was significantly related to POP concentrations in the blubber.