Small Hake Research Articles

Anisakid Nematodes and Potential Risk of Human Anisakiasis through the Consumption of Hake, Merluccius spp., Sold Fresh in Spanish Supermarkets

Nematode parasite species belonging to the Anisakis simplex complex are the most important cause of human anisakiasis through the consumption of (mainly) undercooked, previously not frozen, or conveniently treated fish. In Spain, the consumption of hake has been recognized as an important source of this parasitosis. With the aim of shedding light on the risk factors that can influence the potential risk of human anisakiasis in Spain through the consumption of fresh hake sold by nationwide supermarket chains, a total of 536 small hake specimens belonging to the species Merluccius bilinearis caught off the Northeast American coasts and Merluccius merluccius caught in the Northeast Atlantic and Mediterranean waters was analysed. Anisakids morphologically identified as Anisakis type I were found as the most prevalent and the most abundant species and were considered the main potential cause of human anisakiasis. Intrinsic and extrinsic factors concerning the hake, such as its origin and season of capture, its size, as well as the days passed between its capture and consumption, should be taken into account to avoid this human parasitosis. It is essential that consumers have access to fish label information which should include, as regulated by the European Commission, traceability data.

Feeding habits and trophic status of Merluccius hubbsi along the northernmost limit of its distribution in the South-western Atlantic

AbstractStomach contents analysis and stable isotope results indicate M. hubbsi is a generalist predator that feeds mainly on demersal fishes, followed by crustaceans and cephalopods. Ontogenetic changes in diet were identified, with fish importance increasing in the diet with hake size. Smaller hake (<250 mm) fed mostly on the sepiolid Semirossia tenera (89.45%IRI) and engraulid fish (89.96%IRI). Mid-sized hake (250–300 mm) fed mainly on benthic fish such as Bellator brachychir (95.63%IRI) and euphausiids (56.46%IRI), while larger hake (>300 mm) fed heavily on Dactylopterus volitans (94.80%IRI) and occasionally on a variety of teleosts. Significant correlations between δ13C (P < 0.05), THg (P < 0.001) and hake size occurred, whereas no relationship was observed between δ15N and hake size or δ15N and total mercury. Signatures were lowest in smaller hake with a tendency of increasing with size. Smaller and larger hake were significantly different in δ13C. Differences regarding isotopic niche width were quantified for each size group; trophic diversity and trophic redundancy among them were negligible, but hake >300 mm possibly have a larger feeding plasticity due to the combination of prey from a wide trophic level range.

Efficacy of selective devices in reducing discards in the Nephrops trawl fishery in the Bay of Biscay

Abstract The Nephrops fishery in the Bay of Biscay is an important commercial fishery which generates large amounts of discards owing to the use of small mesh trawls. To reduce discards, French trawlers were equipped with a variety of selective devices, from 2005 onwards. This study examines their efficacy using data from the French on-board observer programme, 2003–2010. Generalized linear models were built for catches, discards, and landings of Nephrops and hake, controlling for the other factors which drive the variability in these variables. A dorsal square-mesh panel meant to let small hake escape did not affect hake catch, but was found to decrease Nephrops catches and discards. Among the devices intended to reduce Nephrops discards, the flexible grid was the most efficient, as it decreased catches and discards in large proportions while increasing landings but this result was supported by a small number of observations; a larger mesh size in the codend (80 mm instead of 70) slightly decreased Nephrops discards; and a ventral square-mesh panel was not found to affect catch or discards of either species. The design of the on-board observer programme was meant to estimate discard amounts, which limited their utilization to investigate factors for discarding.

Hake catchability by the French trawler fleet in the Bay of Biscay: estimating technical and biological components

AbstractMahévas, S., Trenkel, V. M., Doray, M., and Peyronnet, A. 2011. Hake catchability by the French trawler fleet in the Bay of Biscay: estimating technical and biological components. – ICES Journal of Marine Science, 68: 107–118. Several factors affect trawl catchability: (i) gear and vessel technical characteristics, (ii) anthropogenic factors, and (iii) biological factors. The objectives of this study were to assess the relative contribution of each factor to variations in hake (Merluccius merluccius) landings by the French trawler fleet operating on the shelf of the northern Bay of Biscay (ICES Subdivision VIIIa). Using generalized linear models, the impact of technical and anthropogenic factors was evaluated using landings per unit effort (lpue) obtained from logbooks. Variations in hake lpue were explained primarily by anthropogenic factors. For studying the biological components of catchability, the results of a scientific trawl survey in July 2006 involving three similar trawlers of the French trawler fleet were used. Daytime accessibility to large hake was lower than at night, and about zero for small hake (<19 cm). Estimates of spatial variation made using generalized linear mixed models showed a patchy fine-scale spatial distribution, but a random larger-scale distribution of hake over the area surveyed.

Changes in the diet and feeding of the hake Merluccius merluccius at the shelf-break of the Balearic Islands: Influence of the mesopelagic-boundary community

Short spatio–temporal variations in the feeding intensity and the diet of the European hake, Merluccius merluccius, together with the abundance of their potential prey were studied between August 2003 and June 2004 at two locations, northwest (Sóller) and south (Cabrera), off the island of Mallorca (Balearic Islands, Western Mediterranean) at depths between 150 and 750 m. The two areas present different oceanographic conditions. Hake was mainly distributed along the shelf-slope break and the upper slope (between 166 and 350 m) where recruits (TL<18 cm) were dominant. The hake's diet varied as a function of size. Recruits fed mainly on micronektonic prey, and the diet was influenced primarily by seasonality, with two dietary patterns (identified by MDS analyses) corresponding to August–September 2003 (summer) and to November 2003/February–April 2004 (autumn–winter). The summer pattern was consistent with a thermally stratified water column, while November and April were consistent with homogenized temperature and salinity throughout all the water column. The main prey of recruits were the euphausiid Meganyctiphanes norvegica and the midwater fish Maurolicus muelleri in autumn–winter and myctophids (mainly Ceratoscopelus maderensis) in summer. In contrast to recruits, the geographic factor (NW vs. S) was the main factor influencing the diets of post-recruits (TL between 18 and 21.9 cm) and adults (TL⩾22 cm). Hake recruits (and to a lesser extent post-recruits) and their preferred prey occupied different depth ranges during daylight periods. Meganyctiphanes norvegica and Ceratoscopelus maderensis were, for instance, distributed as much as 500 m deeper than hake that had eaten them. All these trends were especially obvious at NW, an area with a more abrupt slope and with a greater influence by northern winter intermediate water (WIW) inflow in early spring than the S area. These factors probably enhanced micronekton aggregation in April, when feeding intensity (stomach fullness) increased among recruits and post-recruits only at NW. All these factors may have a crucial role in the diet, distribution and probably recruitment success of small hake. Biological factors were also important in trophic shifts in the diet and feeding of hake. Multi-linear regression models pointed to a trend of higher fullness with higher hepato-somatic index (HSI). Therefore greater food consumption by hake may enhance its metabolic condition. Within the framework of shelf-break and slope ecology, we show how the ‘boundary’ mesopelagic community inhabiting the middle slope sustains the trophic requirements of hake, a species distributed at shallower depths along the shelf-slope break. Mesopelagic euphausiids and myctophids are often found in the diets of shelf-break fish. Because the boundary mesopelagic community is distributed worldwide, the high levels of fish biomass often found at shelf-slope breaks could be sustained trophically by deeper, offshore mesopelagic communities, an inverse energy transfer from deep to shallow-water marine ecosystems.

The impact of overfishing and El Niño on the condition factor and reproductive success of Peruvian hake, Merluccius gayi peruanus

In this study we examine physiological responses of Peruvian hake ( Merluccius gayi peruanus) to changes in their population structure and physical environment during the period 1971–2004. In particular, we assess the relative investment of energy in growth and/or reproduction of small (20–35 cm) and large (35–50 cm) hake. We calculated the (i) condition (Fulton’s K), (ii) gonad and (iii) gut fullness indices for 42,761 female hakes sampled from commercial landings; these indices indicate fish somatic, reproductive and feeding condition, respectively. Using Generalized Additive Models we then examined potential relationships between these indices and sea surface temperature anomalies and date. Drastic energy exhaustion and a decrease in female hake fecundity were observed during El Niño events. The long-term trend showed a general increase in condition factor and a decrease in gonad index for large hake between 1971 and 2004. Small hake exhibited a different trend with an increase in reproductive activity, which was accompanied by an earlier maturation. We hypothesise that the observed low investment of energy in reproduction by large female hake might be related to the lack of large males, due to a sex-selective fishery and the impact of El Niño. We suggest that fishing diminished hake reproductive capacity, modified the sex ratio in favour of females and increased population vulnerability to environmental stress, in particular to the El Niño. The impact of multidecadal variability and predators like the squid, Dosidicus gigas, remain unresolved until longer time series become available.

Bathymetric preferences of juvenile European hake (Merluccius merluccius)

Abstract Bartolino, V., Ottavi, A., Colloca, F., Ardizzone, G. D., and Stefánsson, G. 2008. Bathymetric preferences of juvenile European hake (Merluccius merluccius). – ICES Journal of Marine Science, 65: 963–969. The concept of a recruit is a basic notion in fisheries science, but it is still far from being an unequivocal term, and many diverse, even ambiguous, definitions can be found in the literature. We propose a more objective and biologically meaningful way to define the length range of recruits for species that have clear bathymetric segregation during the early stages of their life cycle. The bathymetric distribution of juvenile European hake was studied by fitting a thin plate spline to data from the national autumn trawl survey. Hake showed a stable pattern of depth preference in the 6-year dataset examined. Small hake had the greatest preference for depths of 170–220 m and appeared to move slightly deeper when they reached 10-cm total length. Larger hake persisted on the continental shelf with a preference for water 70–100 m deep, especially when they reached 18–20 cm long. The length at migration was defined as the length at which the minimum depth preference was shown, and it ranged between 13.2 and 15.8 cm depending on the year. There was a relationship between length at and depth of migration, and we provide a full description of the depth preference of juvenile hake, and test the effectiveness of the analytical approach used.

Ontogenetic and spatial variation in the diet of hake (Merluccius merluccius) in the Bay of Biscay and the Celtic Sea

Abstract Mahe, K., Amara, R., Bryckaert, T., Kacher, M., and Brylinski, J. M. 2007. Ontogenetic and spatial variation in the diet of hake (Merluccius merluccius) in the Bay of Biscay and the Celtic Sea. – ICES Journal of Marine Science, 64: 1210–1219. Analysis of the diet of trawl-caught hake (Merluccius merluccius) from three locations in the Bay of Biscay and the Celtic Sea in autumn 2001 showed that small hake fed almost exclusively on crustaceans (mainly euphausiids), but that there was a significant shift towards a fully piscivorous diet in hake &gt;23 cm. A change in fish prey was also size-dependent, because smaller hake (&lt;30 cm) preyed on small pelagic fish (3–12 cm), such as horse mackerel, anchovy, and pilchard, and larger hake on larger demersal prey (12–23 cm), such as blue whiting. There was a significant positive relationship between hake and fish prey length. In terms of fish prey selectivity, hake exhibited particular preference for small pelagic prey (anchovy, pilchard, and argentine) and for other hake. The diet did not generally reflect fish prey availability. Although horse mackerel and blue whiting were the two most abundant fish prey species in the environment, they were not positively selected by hake. Cannibalism accounted for a non-negligible part of the diet and was observed mainly in large hake (&gt;30 cm). For all sizes analysed, conspecifics constituted 19.2%W of the diet and the frequency of occurrence of hake in the stomachs was 10.53%. Most hake prey were 0-group juveniles (&lt;20 cm). Hake cannibalism appeared to be influenced mainly by the abundance of juveniles and the overlap between distribution patterns of juveniles and adults.

Diet of Cape fur seals Arctocephalus pusillus pusillus at three mainland breeding colonies in Namibia. 2. Temporal variation

Scat analysis was used to assess temporal variability in the diet composition of Cape fur seals Arctocephalus pusillus pusillus from three breeding colonies in Namibia (January 1994 to April 2002). The diet displayed significant inter- and intra-annual variation in composition at each of the study colonies. The diet was not predictable on an annual pattern, and little consistent seasonality was apparent at each of the study sites. However, some prey species tended to display some seasonality, possibly as a result of their life-history patterns. At the Cape Cross colony, small Cape hake Merluccius spp. in the diet coincided with their spawning season. At the Atlas-Wolf Bay and Van Reenen Bay colonies, lanternfish Lampanyctodes hectoris were most prevalent in the diet during the upwelling season (August–January). Outside that period, pelagic goby Sufflogobius bibarbatus were most abundant in the diet at those colonies. This pattern may be a result of the gobies' southwards migration from northern Namibian waters where smaller goby are dominant in the diet at the Cape Cross colony in the upwelling season. The prevalence of Cape horse mackerel Trachurus trachurus capensis in the diet at Cape Cross was coincident with the pelagic phase of juvenile horse mackerel.

Recruitment and post-settlement growth of juvenile &lt;i&gt;Merluccius merluccius&lt;/i&gt; on the western Mediterranean shelf

Young-of-the-year European hake (Merluccius merluccius) were sampled during four seasonal cruises between November 1998 and September 1999. The greatest numbers and biomass were found in spring 1999. Some 73% of juvenile fish in terms of number, and 81% in terms of biomass, were caught at depths between 60 and 160 m on the outer western Mediterranean shelf, where the water temperature ranged between 13.5 and 14°C. The length composition of samples showed there to be small hake all year around, with modes between 7 and 11 cm total length depending on the season. Otolith analysis was used to establish age at settlement (62.7 days) and to determine seasonal growth. The monthly growth rates ranged from 1.2 cm month-1 for juvenile hake captured on February 1999 to 2.5 cm month-1 for ones captured in June. The growth rates are related to survival, as was shown by the calculated hatch dates and relative abundances of recruits. This work provides information on the first year of life, recruitment and growth processes in an important species of the Mediterranean demersal ecosystem which is heavily exploited by a recruitment fishery.

Relationships among vertically structured in situ measures of turbulence, larval fish abundance and feeding success and copepods on Western Bank, Scotian Shelf

Using vertically stratified data of the abundance of silver hake (Merluccius bilinearis) larvae and concentrations of copepods collected in the field, we examine relationships among the vertical distribution of larval fish, their potential prey, feeding success and water column turbulence. Water column turbulence and associated stratification parameters were estimated from: (i) in situ measures of turbulent kinetic energy dissipation (ɛ) provided by an EPSONDE profiler; (ii) in situ wind speed; (iii) the Richardson number (Ri); and (iv) the buoyancy frequency (N2). Small (&lt; 5 mm total length) silver hake were more abundant in the least turbulent waters (i.e. at a minimum in the rate of dissipation of turbulent kinetic energy, ɛ &lt; 10–7 W kg−1; Ri &gt; 0.25; N2 &gt; 0.001 (rad s–1)2). Partial correlations amongst ɛ, N2 and small hake larvae were significant only for N2. The abundance of larger (&gt; 5 mm total length) hake larvae was positively correlated with depth and was not associated with either ɛ or N2. Vertical distributions of three potential prey (classified by stage) were variable. Early stage copepodids were positively correlated with N2 and negatively correlated with ɛ. We found no evidence of diel distribution patterns for small (&lt; 5 mm total length) hake larvae or for any of the developmental stages of the copepods examined. Neither estimate of water column turbulence inferred from wind speed nor from Ri was meaningfully related to in situ estimates of ɛ or to larval fish abundance. Feeding success, measured either as prey items (gut)–1, average prey length, or total prey volume (gut)–1, was not related to predicted encounter rates between days. However, the average prey length (gut)–1 was significantly (P &lt; 0.01) related to water column turbulence. These conflicting results suggest that the relationship between larval feeding and the environment is more complicated than assumed. We conclude that without substantial high resolution in situ examination of the relationship between the vertical distributions of turbulence, larvae and their prey, the growing acceptance in the secondary literature that turbulence has a positive and biologically meaningful effect on trophic interactions between fish and their zooplankton prey (a generalization based largely on modelling and laboratory experiments) is premature.

Arsenic in cooked seafood products: study on the effect of cooking on total and inorganic arsenic contents.

Total and inorganic arsenic contents were analyzed in cooked seafood products consumed in Spain during the period July 1997-June 1998: hake, meagrim, small hake, anchovy, Atlantic horse mackerel, sardine, bivalves, crustaceans, squid, and salted cod. Various cooking treatments were used (grilling, roasting, baking, stewing, boiling, steaming, and microwaving). The results obtained were compared statistically with those found previously in the same products raw, and they showed that after cooking there was a significant increase in the concentration of total arsenic for salted cod and bivalves, and in the concentration of inorganic arsenic for bivalves and squid. The mean content of inorganic arsenic was significantly higher in bivalves than in any other type of seafood. For the Spanish population, the mean intake of total arsenic estimated on the basis of the results obtained in this study is 245 microg/day. The intake of inorganic arsenic (2.3 microg/day) represents 1.7% of the World Health Organization provisional tolerable weekly intake (PTWI), leaving an ample safety margin for this population, which has a very high consumption of seafood.

Distribution of hake ( Merluccius merluccius, Linnaeus, 1758) in the Bay of Biscay and the Celtic sea from the analysis of French commercial data

Hake landings and effort data provided by the French otter trawl fleets exploiting the Celtic sea and Bay of Biscay fishing grounds were used for years 1992–1994. Monthly catch rates of five hake weight market categories were calculated and used as input in a correspondence analysis and hierarchical ascending classification procedure to describe the spatio-temporal distribution of hake in the Celtic sea and the Bay of Biscay. Results show a great difference in hake catch composition between the two zones. The higher proportion of small hake in the Bay of Biscay can be explained by the use of a minimum mesh of size 65 mm instead of 80 mm in the Celtic sea and the existence of a hake nursery coinciding with the muddy bottom of Nephrops fishing grounds in the northern part of the Bay of Biscay. Adult hake were found relatively more abundant in the shallow water of the eastern Celtic shelf from April to November. Oldest fish seemed to move westwards at the end of the year. They congregate for spawning along the slope and on the shelf in the north-western part of the Celtic sea from February to April–May. There is no evidence that young adult hake follow the same migratory pattern but they were found in abundance along the slope in the north of the Bay of Biscay during autumn and winter months.

Reconstructing reciprocal M vectors from length cohort analysis (LCA) of commercial size frequencies of hake, and fine mesh trawl surveys over the same grounds

Results of length cohort analysis of commercial landings with fine mesh trawls of small hake from Viareggio, Ligurian Sea, are compared with the size frequency of contemporaneous randomized trawl surveys on the fishing grounds of the same port under two assumptions: (1) constant M; (2) M as a reciprocal function of age obtained from an earlier analysis. The second comparison showed a closer relationship between predicted and actual numbers of individuals on the grounds. A third approach used the same two data sets to find a “best fit” for a reciprocal M-at-age relationship of the type previously described by Caddy. This M vector, and the F-at-age values lead to, appear to be more reasonable than those obtained under “constant M” assumptions.

Diel variability in bottom trawl catches and feeding activity of the Cape hakes off the west coast of South Africa

The diel variability in bottom trawl catches and the feeding patterns of the Cape hakes Merluccius capensis and M. paradoxus were investigated during thirteen 28-h experiments in winter and summer between 1984 and 1990 within the same locality off the west coast of South Africa. Considerable variation was found in the diel differences in the catches, but day-time numbers and mass were generally greater than at night. Catch rates of M. capensis were significantly different in nine experiments whereas five experiments yielded significant differences in M. paradoxus. For small hake, especially M. paradoxus, euphausiids were eaten more frequently in summer and mesopelagic fish were of more dietary importance in winter. Hake-on-hake predation was a prominent feature in M. capensis, especially in summer when larger fish were caught at the study site. In the majority of cases, the size composition of M. capensis was not significantly different between the day and night catches. By contrast, diel size differences were generally found in M. paradoxus, but with no consistent pattern. There was little indication of any diel feeding periodicity in either hake species, with up to one-third of the hake examined with food in their stomachs having recently fed, regardless of time of day or night. The diet composition indicated that hake move into midwater at night in response to similar movement of their prey.

Effekt des Gefrierens auf die?-Hydroxyacyl-CoA-dehydrogenase (HADH)-Aktivit�t von Fischfleisch

Changes in the β-hydroxyacyl-CoA-dehydrogenase (HADH) activity of squid (Loligo vulgaris), mackerel (Scomber scombrus), tuna (Thunnus alalunga), sea bream (Pagellus centrodontus), sole (Solea solea), hake and small hake (Merluccius merluccius) meat due to freezing treatment at −10° C, −18° C, −35° C, −80° C or −196° C were investigated. With the exception of the small hake, the HADH activity of aqueous extracts from meat was significantly higher (p<0.0001) in all frozen/thawed fish species studied than in unfrozen animals because during freezing there was a release of HADH. HADH activity values of frozen/thawed squid, unfrozen mackerel, frozen/thawed and unfrozen sea bream and unfrozen hake were affected by the storage time in crushed ice.

Feeding selectivity of juvenile Cape hakeMerluccius capensisin the southern Benguela

Prey selectivity and feeding behaviour of juvenile shallow-water Cape hake Merluccius capensis are investigated on the basis of material collected at two sites of contrasting feeding regimes in coastal waters off the South African west coast. Hake collected from a site abundant in zooplankton fed preferentially on relatively large crustaceans (amphipods, euphausiids and Pasiphaea semispinosa), but apparently ignored the smaller copepods and translucent prey (chaetognaths), despite these taxa being both numerically and by mass the dominant potential prey items. At a site dominated by recruits of anchovy Engraulis capensis, the hake were almost exclusively piscivorous. Small hake (10–25 cm) migrated vertically into subsurface layers to feed on anchovy, whereas larger fish appeared to remain near the bottom where cannibalism was prevalent. The present observations demonstrate the importance of vertical migratory behaviour in the foraging strategy of juvenile M. capensis.

The diet of Patagonian hake Merluccius australis polylepis and its daily ration of Patagonian grenadier Macrouronus magellanicus

The diet of the Patagonian hake Merluccius australis polylepis in 1986 was determined by analysis of stomach samples collected from commercial trawl catches. The major prey items were Patagonian grenadier Macrouronus magellanicus and, to a lesser extent, southern blue whiting Micromesistius australis. Large (81–100 cm) hake are mainly piscivorous and consume more grenadier than smaller (51–80 cm) hake. The smaller hake feed both on fish and invertebrates. There was no difference by sex in terms of stomach contents. The daily feeding cycle was also investigated from samples collected during 1991. Hake feed principally on 1-, 2-, and 3-year-old grenadier, which they seem to catch mainly at night. The daily ration of grenadier was between 0,043 and 0,26 per cent of body mass (1,692–9,849 g). The results are similar to those for other hake species in terms of composition of the diet, daily feeding cycle and daily ration.

Size-Dependent Spatial Distribution of Hake (Merluccius capensis and Merluccius paradoxus) in Namibian Waters

Data on hake (Merluccius capensis and Merluccius paradoxus) abundance along the Namibian coast showed both species to have strongly aggregated spatial distributions. In addition, average fish size increased with depth, suggesting that the formation of hake aggregation is based on size-dependent shoaling behaviour. Hake spacing was size dependent with areal fish density and biomass being scaled to the −5 and −2 power, respectively, of fish length. The equations describing the size dependence of the areal fish density were log density (fish∙m−2) = 5.06-4.91 log size (cm) for M. capensis and log density (fish∙m−2) = 5.28-4.74 log size (cm) for (M. paradoxus). The maximum areal densities, presumably corresponding to those within the shoals, exceeded those described by the equations above by 20- and 13-fold for M. capensis and M. paradoxus, respectively. The size dependence of hake spacing implies that fishing pressure targeting aggregates of small hake (i.e. shallow shoals) should have a disproportionate effect on fish mortality and recruitment compared with similar fishing pressure targeting aggregates of larger hake (i.e. deep shoals).

The Occurrence of the Blood Fluke, Aporocotyle spinosicanalis Williams, 1958 in European Hake, Merluccius merluccius (L.) caught off the British Isles

Of the 1,090 hake, Merluccius merluccius (L.), examined for Aporocotyh spinosicanalis, 323 were infected. Only adult flukes were found and these in the heart and bulbus arteriosus only; this habitat specificity and the apparent strict specificity of the fluke to hake are briefly discussed. The occurrence of from 1 to 5 flukes in each infected fish was common but up to as many as 60 were recorded. The incidence of infection is high in hake from shallow water in some areas to the west of Scotland; a particularly high incidence was found in the Minches and Sea of the Hebrides area. The incidence of infection was very low to the southwest of the British Isles and off Hartlepool in the North Sea; only 1 of 82 fish from these regions was infected. The possible use of A. spinosicanalis as a biological tag is discussed. A significant difference was found in the incidence of infection in hake of different length groups, the most heavily infected being those measuring 26 to 55.9cm.; small hake (25.9 cm. and below in length) from shallow water showed a low incidence of infection. Speculations are made on the possible course of the life-cycle of A. spinosicanalis. There was no significant difference in the distribution of the fluke in male and female fish and no obvious effect on the condition of the host was observed.