Transmission models for the fish pathogen Ichthyophonus: synthesis of field observations and empirical studies

Empirical studies have demonstrated that Ichthyophonus is transmitted among piscivores via consumption of infected prey; however, this unidirectional mode of transmission from small to large fish cannot sustain Ichthyophonus within a population. To circumvent this problem, Ichthyophonus evolved an infective waterborne cell that has been shown to infect both fresh- and saltwater fish. Successful transmission of Ichthyophonus via a waterborne stage is linked to the proximity of infected and susceptible individuals, a condition met when the two groups occupy the same habitat. It is posited that this occurs during annual inshore migrations when herring (Clupea spp.) enter areas occupied by infected demersal predators. A plausible transmission scenario is that during inshore excursions, planktivores are exposed to infective waterborne cells shed by demersal piscivores. Once planktivores are infected, the parasite is recycled when consumed by predators. This model is supported by reports of ichthyophoniasis increasing in herring populations at the time of inshore migration. The possible role of an intermediate host for Ichthyophonus, as well as evidence for a free-living stage in its life cycle, is presented.

Inshore migration of tropical glass eels (Anguilla spp.) in Lambeso River, Aceh Jaya District, Aceh Province, Indonesia

The objective of the present study was to evaluate the migration time of glass eels (Anguilla spp.) in the estuary of Lambeuso River, Aceh Jaya District, Indonesia. The survey was done in March and June 2015. The sampling location was determined based on an initial survey during February 2015 by considering the river condition. Based on initial survey there are no glass eels were recorded during noon time, and therefore the sampling was focused at night. The sampling was done four times a month (weekly basis) for three months (12 times in total) using trap nets based on Hijri Calendar. The trap was settled up to opposite direction of tide (seaward) from 18.00 PM to 06.00 AM and the catches glass eels were monitoring one-hour interval. A total of 131 glass eels were sampled during the study, where the samples were only caught on first (new month) and fourth week (old month) base on Hijri Calender during spring tide and no glass eels were sampled during second and third weeks. It was concluded that the migration time of the glass eels (Anguilla spp.) in Lambeso Rivers is during the dark moon at the new and old month of Hijri Calendar

The horizontal migration of hammerhead sharks along the southern Brazilian coast, based on their exploitation pattern and considerations about the impact of anchored gillnets activities on these species

Between 1995-2009 hammerhead sharks were sampled from the landings ofthe industrial fleets based in the harbours of Itajaí and Navegantes, SC State,and Ubatuba, SP State, Brazil. In this case, fishing boats which operated with gillnetslonglines and trawls along the southern Brazilian Economic Exclusive Zone and internationaladjacent waters were targeted. A total of 2483 and 353 S. lewini and S. zygaena carcasses respectively were sexed, measured and converted to total lengths (LT). Additionallyinformation about, year, season, latitude/longitude and local depth (m) from the catches,by fishing category, were obtained. During the considered period, intense fishing mortalityover pups was caused by gillnets and trawls operating on shallow waters (≤20m) and overjuveniles along the continental shelf (>20m and ≤200m). Additionally, adults were exploitedby driftnets and longlines along the shelf border and slope (>200m). Therefore,both hammerhead species are exploited at all life-stages and throughout their migratory circuit.This includes during their inshore-offshore migration while they are growing from pupsto juveniles and as the offshore-inshore migration of pregnant females to pupping areas inshallower waters. This apparently unsustainable exploitation pattern, over different sizeclasses (newborns-juveniles-adults), and the economic pressure caused by the internationalfin market, is one of the reasons for population declining of these two species in southernBrazil. Non fishing zones for the hammerheads, protecting their migratory circuit, which isdriven by their growth pattern and reproduction, are necessary. Additionally, fishing effortreduction and a control over the international fin market are recommended.

BIODIVERSITY, DISTRIBUTION, AND ABUNDANCE OF THE TROPICAL ANGUILLID EELS IN THE INDONESIAN WATERS

In order to understand biodiversity, distribution, and abundance among the tropical anguillid eels in the Indonesian waters, inshore migration mechanism of the juvenile anguillid eel (glass eel) to the estuaries of western, central, and eastern region of Indonesian waters were examined using both morphology and genetic analyses. A total of 9 species/sub species of anguillid eels (Anguilla bicolor bicolor, A. nebulosa nebulosa, A. bicolor pacifica, A. interioris, A. borneensis, A. celebesensis, A. marinorata, A. obscura and A. megastoma) were recognized to recruit at the mouth of 15 rivers through Indonesian archipelago. Species/subspecies diversity and distribution of recruiting juveniles differs in the estuaries of each region. In the western region that represented by estuary of Krueng Aceh, Batang Antokan, Air Kertaun, Cibaliung, Citanduy, Progo, and Pacitan Rivers, three species and sub species (A. bicolor bicolor, A. nebulosa nebulosa and A. bicolor pacifica) were found. In the central region that represented by estuary of Mahakam, Palu, Dumoga, Poigar, Bone, and Poso Rivers, five species and sub species (A. borneensis, A. celebesensis, A. marinorata, A. bicolor pacilica and A. interioris) were found. In the eastern region that represented by estuary of Akelamo and Pami Rivers, four species (A. marinorata, A. interioris, A. obscura and A. megastoma) were found. During the 6 months investigation from May to October 2005, abundance of the juveniles was higher in the central region compared with western and eastern regions. These results were suggested that inshore migration mechanism of tropical anguillid eels recruiting in tropical estuaries of Indonesian waters differs among regions.