Population structure of the monogenean, Paramazocraes thrissocles (Mazocraeidae) on the gills of clupeoid fish, Thryssa mystax of Visakhapatnam coast, Bay of Bengal

An investigation was undertaken on the population biology of the mazocraeid monogenean

Sympatric Clupeoid Fish Larvae in the Northeastern Mediterranean: Coexistence or Avoidance?

The summer (July 2002 and 2003) larval concentrations of two commercially important clupeoid species (order: Clupeiformes), the European anchovy (Engraulis encrasicolus) and round sardinella (Sardinella aurita), were measured in Kavala Gulf (northern Aegean Sea), in order to examine their distribution patterns. Anchovy was generally most abundant, reaching 13 852 larvae 10 m−2 in 2003 and occurred in more stations compared to round sardinella. Despite the spawning of both species occurring across the entire gulf, the general spatial distribution of their larvae was different, with European anchovy larvae occupying the entire gulf and round sardinella larvae mainly concentrated at offshore stations. The reason proposed for the spatial segregation of their larvae is direct competition for resources. Yet, coexistence of the two species was observed in frontal areas with abundant food resources that prevent competition.

Morphological and systematic reassessment of †Knightia brasiliensis Woodward, 1939 (Teleostei: Clupeiformes) from the Pliocene of Parnaíba Basin, northeastern Brazil

†Knightia brasiliensis, a small clupeoid fish found in the Tertiary beds of Nova Iorque, State of Maranhão (Brazil), is morphologically redescribed in detail. It is separated from nominal species of †Knightia, including the type-species †Knightia eoceana from the Lower Eocene of Wyoming, mainly by the absence of dorsal scutes, presence of two supramaxillae, and one epural, and is therefore placed in a new genus, †Paleopiquitinga gen. nov. The caudal skeleton of †Paleopiquitinga gen. nov. shows some advanced features (one epural, parhypurapophysis, and pleurostyle) in comparison with other well-known fossil clupeomorphs from the Cretaceous and Tertiary of South America and Africa, and a combination of features indicates the placement of †Paleopiquitinga gen. nov. within the family Clupeidae. Although uncertainties about polarity of characters within the Clupeidae render the relationships of †Paleopiquitinga gen. nov. difficult to establish at present, certain features indicate a close relationship with the extant Atlantic and East-Pacific genus Lile.

A new marine clupeoid fish from the Lower Cretaceous of the Sergipe-Alagoas Basin, northeastern Brazil

Clupeomorph fishes are largely diversified and widespread in Cretaceous strata of northeastern Brazil. They are represented by basal clupeiforms, †ellimmichthyiforms, and advanced clupeoids. In this paper, a new clupeoid fish, †Nolfia riachuelensis sp. nov., is described based on a specimen found in marine shale yielded in the Taquari Member (Albian) of Riachuelo Formation, Sergipe-Alagoas Basin. Although partially preserved (most of skull is lacking), the fish shows many informative characters, particularly in the axial skeleton. The fish is morphologically very similar to †Nolfia kwangoensis, a clupeoid fish originally described from marine deposit from the Upper Cretaceous (Cenomanian) of Kipala, Democratic Republic of Congo, with which it shares: 18 caudal vertebrae; long and cylindrical pleural ribs; posteriormost pleural ribs supported by long parapophyses and gradually decreasing in size posteriorly; very reduced ural centra; presence of long and distally congruent neural spines of third, second, and first preural centra; three uroneural bones (the first probably forming the pleurostyle). Otherwise, †Nolfia riachuelensis sp. nov. differs from other clupeomorphs by a unique combination of features. The number of supraneural bones, aligned rod-like postcleithra, less than 30 rays in the anal fin, and derived absence of dorsal scutes indicate its placement within Clupeidae. As far as is known, †Nolfia riachuelensis sp. nov. is the most ancient clupeoid fish known from the fossil record.

Pacific herring respond to simulated odontocete echolocation sounds

There has been a long-running debate as to if and how clupeoid fish, such as herring (Clupea sp.), respond to anthropogenic sound. Anatomical and physiological investigations have shown that members of the clupeoid suborder have highly developed hearing extending into ultrasonic frequencies and behavioural studies suggest that they respond to many sounds. However, only recently have the selective forces that have driven the evolution of this keen sense and behavioural repertoire played a major part in the debate. One explanation is the adaptation to predation from echolocating cetaceans. In this study, we investigate the responses of adult Pacific herring (Clupea pallasii) to broadband biosonar-type sounds with high-frequency similarities to those produced by odontocete cetaceans. Exposures to these sounds in an indoor tank and sea cage caused feeding fish to cease, drop in the water column, and begin to school actively. Fish already schooling dropped in the water column and increased their swimming speed. Exposures to electronic silence and an acoustic deterrent device for marine mammals did not elicit such responses. We discuss the potential suitability of the observed manoeuvres for avoidance of foraging odontocetes and consider their relevance for human-related fishing activities.

Seasonal variation in the species and size composition of the clupeoid assemblages in Western Port, Victoria

The size composition of three species of clupeoid fish was monitored from monthly samples taken between May 1992 and April 1994 in Western Port, Victoria. Anchovy and pilchard were the dominant species in most samples and sandy sprat were occasionally common. Seasonal variations in catches indicate that adult clupeoids are temporary inhabitants in Western Port, migrating into the bay between October and December and leaving between February and June. Juvenile anchovy and pilchard were common in catches between February and April, indicating that Western Port serves as a nursery area for both species. Sizes of adult anchovy and pilchard collected in Western Port were at the lower end of the known range and these probably represent a single age-group of young adult fish. Comparisons with published data from Bass Strait and Port Phillip Bay show the importance of different habitats for different sizes of clupeoids in western Victoria.