Epilithic biofilm as a key factor for small-scale river fisheries on Caribbean islands

Abstract

Numerous freshwater species are consumed or exploited through artisanal fisheries in the rivers of the islands of Guadeloupe, French West Indies. Autochthonous production of organic matter is limited in these flowing rivers and is mainly represented by scarce filamentous green algae and an abundant epilithic biofilm growing on wet stones in the river bed. Stable isotope analysis was used to quantify the relative importance of biofilm and other riverine allochthonous and autochthonous food sources in the diet of tropical shrimps (Palaemonidae, Atyidae and Xiphocarididae) and fishes (Gobiidae and Eleotridae) consumed by the local people. The epilithic biofilm was exploited by most species, constituted an important source of autochthonous carbon and was an important source of organic matter production at the base of freshwater food webs in Caribbean rivers. Biofilm percentages in the diet reached 32% for molluscs, 85% for atyid shrimps, 29% for xiphocaridid shrimps, 14% for palaemonid shrimps and 13% for fish. Assessment of biofilm in nine rivers showed that blue and red cyanobacteria were quantitatively dominant with a moderately rich diatom flora. These results address the interactions between river biofilm and Caribbean freshwater fauna where trophic links between consumers and their potential resources have poorly been documented. (Résumé d'auteur

Hydraulic Preferences of Shrimps and Fishes in Tropical Insular Rivers

“…The fish of the subfamily of Sicydiinae in the two regions ( Sicydium sp., C. acutipinnis and S. lagocephalus ) prefer fast‐flowing and shallow habitats. Their hydraulic preferences are probably linked to the presence of periphytic biofilm whose quality and development are conditioned by bed shear stress and light, respectively (Julius et al ., ; Lefrançois et al ., ; Tabouret et al ., ). The hydraulic preferences of S. lagocephalus and C. acutipinnis are comparable with those given by the logistic models built by Teichert et al .…”

“…The latter two models permit appreciating the transferability of the results between rivers. Different criteria were used to define two groups of surveys in M4 (with comparable numbers): the season of low and high flow in the Caribbean, the years before and on or after 2009 in the Caribbean and the years before and on or after 2005 in the Indian Ocean, the altitude (≤ or >165 m in the Caribbean; < and ≥80 m in the Indian Ocean), the wind coast exposure Habitat use and feeding groups are summarized from information detailed in Coat et al (2009Coat et al ( , 2011, Keith et al (1999), Lim et al (2002) and Monti et al (2010). Abbreviations for feeding guilds are as follows: F for filter feeding, H for herbivore, D for detritivore, O for omnivore.…”

Organochlorine pollution in tropical rivers (Guadeloupe): Role of ecological factors in food web bioaccumulation

“…1, which describes the food web structure examined during the dry (part a) and the wet (part b) seasons (data redraw from Coat et al, 2009 andLefrançois et al, 2010 Details regarding trophic relationships and diets were given in previous papers (Coat et al, 2009;Lefrançois et al, 2010). Table 2 Average residue levels (µg kg -1 w.w.) of chlordecone (chlord.…”

“…The determination of OC bioaccumulation and subsequent transfer within a food web first requires the identification of trophic interactions between species. The structure of the stream food web in Guadeloupe has been described during the dry (December to May) and the wet (June to November) seasons, using stable isotope analysis combined with literature dietary data (Coat et al, 2009;Lefrançois et al, 2010).…”

Otolith microchemistry inSicydium punctatum: indices of environmental condition changes after recruitment

“…Lefrançois et al (2011) showed that a mean of 25 to 31% of S. punctatum diet is provided by the epilithic biofilm growing on wet stones on the river bed in Caribbean rivers. The colonisation of biofilm on the substrate takes 2−3 weeks.…”