Search

This paper presents experimental results on the voracity and foraging behaviour of the European sea bass, Dicentrarchus labrax adults kept in captivity fed a commercial broodstock feed suitable for the species. The results show that the species is a very aggressive predator even after 2 decades of captivity actively competing for food. The primary sensory stimulus to attack the food particles is vision. The number of food particles in the water also affect the foraging behaviour of the fish. As the number of pellets offered simultaneously increases from 10 to 50, so increases the number of missed attempts to consume the particles as well as the number of collisions between individuals attempting to consume the same particle. However, when the number of pellets is more than 30, the dispersion caused by the fish movements is greater and the fish are able to consume more pellets in one pass and therefore, the amount of pellets is consumed sooner. Conceptualising our results for the Mediterranean farming of the sea bass, we consider that its foraging behaviour as described in his paper should be considered as an indicator of good welfare of the farmed fish. In addition, the species foraging behaviour may have important undesirable side effects such as the infliction of trauma due to biting between fish during collisions as well as the loss of food particles through the cage nets during feeding due to the turbulence the fish create by attacking the food particles and missing., U radu su opisani eksperimentalni rezultati o proždrljivosti i grabežljivosti lubina, Dicentrarchus labrax hranjenog komercijalnom hranom u zatočeništvu. Rezultati ukazuju da je lubin vrlo agresivni predator unatoč 20-godišnjem zatočeništvu. Primarni osjetilni senzor za napad na čestice hrane je vid. Broj čestica hrane u vodi također utječe na potragu za česticama hrane. S porastom broja peleta od 10 do 50, povećava se i broj neuspješnih pokušaja uzimanja hrane, kao i broj sudara riba u bazenu. Međutim, kada je broj peleta hrane veći od trideset, raspršenost hrane u bazenu uslijed kretanja riba je veća, zbog čega ribe mogu u jednom napadu pojesti više peleta hrane, te se hrana brže pojede. Primjena ovih rezultata u mediteranskom uzgoju lubina može se razmatrati s aspekta dobrobiti uzgajanih riba. Opisano ponašanje riba kod hranidbe može imati i važne nepoželjne učinke, kao što su ozljede uslijed međusobnih ugriza i sudara, kao i do gubitka hrane radi propadanja kroz kavez uslijed turbulencije koju ribe stvaraju napadima i promašajima čestica hrane.

Sphedanolestes minusculus Bergroth lays pale yellow eggs in batches. Eggs are glued to each other and to the substratum with cementing material. The average number of eggs per female was 63.33 ± 21.77. The eggs hatch in 7.80 ± 0.41 days. The average developmental period from I instar to V instar was 48.43 ± 7.39days. The longevity of the male (80.16 ± 5.23) was shorter (96.77 ± 11.88) than that of the female. The preoviposition period was 12.55 ± 3.43 days and the male and female sex ratio was 1: 1.5. The innate capacity of natural increase (rc) was 0.061 with a gross reproduction rate (mx) of 91.671 females per female. Mean length of generation (Tc) was 76.310 days. Redescriptions of adult and descriptions of egg and nymphal instars are given with illustrations. Predatory and mating behaviour exhibited sequential events as in other reduviids. Prey-deprived predators took less time to approach, capture and pin the prey. Individuals of S. minusculus collected from three different ecological and geomorphological habitats viz., Olavakod tropical rainforest, Sunkankadai scrub jungle and Aralvaimozhi semiarid zone exhibited pronounced diversities in their oviposition pattern, hatchability, incubation and stadial periods, nymphal mortality, adult longevity and sex ratio. These diversities are considered a specially adapted biological function collectively called ecotypism., Sphedanolestes minusculus Bergroth polaže blijedo žuta jaja u gomilicama. Jaja su ljepljivom tvari slijepljena međusobno kao i za podlogu. Srednja vrijednost broja jaja po ženki je bila 63,33 ± 21,77. Ličinke su se izvalile u 7,80 ± 0,41 dana. Srednja vrijednost razvojnog perioda od I do V stadija bila je 48,43 ± 7.39 dana. Dužina života mužjaka (80,16 ± 5,23) bila je kraća (96,77 ± 11,88) nego ženki. Preovipozicija jaja je trajala 12,55 ± 3.43 dana a omjer između mužjaka i ženki je bio 1:1,5. Urođen, svojstven kapacitet prirodnog porasta (rc) je bio 0,061 s maksimalnim omjerom reprodukcije (mx) od 91,671 ženki. Prosječna dužina života jedne generacije (Tc) bila je 76, 310 dana. Ponovo su opisani odrasli, a na novo jaja i ličinački stadiji prikazani slikama. Složeno predatorsko ponašanje i ponašanje tijekom parenja slijedilo je pravilan tok kao kod drugih vrsta porodice Reduviidae. Ovi predatori su brzi u lovu i pridržavanju ulova. Jedinke Sphedanolestes minusculus su bile sakupljane u tri različita ekološka i geomorfološka staništa: Olavakod - tropska kišna šuma, Sunkankadai - guštara đungle i Aralvaimozhi - semiaridna zona. Opisane su različitosti u: njihovim ovipozicijskim uzorcima, izlijeganju jaja, vremenu inkubacije, trajanju razvojnih stadija, ličinačkoj smrtnosti, dužini života odraslih, te omjeru spolova. Te razlike u opisanim karakteristikama smatraju se posebno prilagođenim biološkim funkcijama koje zajednički nazivamo ekotip.