Size-related Predation Research Articles

Post-escape dispersal of juvenile Atlantic cod Gadus morhua from Norwegian fish farms and their potential for recapture

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 3:107-116 (2013) - DOI: https://doi.org/10.3354/aei00051 Post-escape dispersal of juvenile Atlantic cod Gadus morhua from Norwegian fish farms and their potential for recapture R. M. Serra-Llinares1,2,*, R. Nilsen1,2, I. Uglem3, P. Arechavala-Lopez4, P. A. Bjørn1,2, C. Noble1 1Nofima, Muninbakken 9-13, 9291 Tromsø, Norway 2Institute of Marine Research, PO Box 6404, 9294 Tromsø, Norway 3Norwegian Institute of Nature Research, Tungasletta 2, 7485 Trondheim, Norway 4Department of Marine Science and Applied Biology, University of Alicante, PO Box 99, 03080 Alicante, Spain *Email: rosa.maria.serra.llinares@imr.no ABSTRACT: The escape of fish from sea-based aquaculture facilities is regarded as a potential environmental threat and is one of the biggest challenges the industry has faced in recent years. In addition to preventing escapes by improving farming operations and procedures, effective and operational routines are needed for recapturing fish should an escape occur. This study investigated the post-escape dispersal of juvenile Atlantic cod Gadus morhua L. from commercial sea cages in coastal Norway using acoustic telemetry. It also assessed the efficacy of different techniques (e.g. cod pots, fyke nets, and gill nets) for recapturing escaped fish. Results suggest that escaped juvenile cod can experience a high size-related predation pressure immediately after escape due to high numbers of large fish aggregating around the cages. Consequently, the escapees rapidly disperse from the farms and seek shelter in littoral areas. Once in shallower waters, they stay relatively close (<10 km) to the farm during the first 2 mo following an escape. This suggests a high potential for recapture if the effort is focused on the littoral area and not in the immediate vicinity of the farm. No escapees were caught using live recapture methods, and a low number of recaptures (<5%) were achieved with gill nets deployed in littoral areas. Moreover, high by-catch rates and a subsequent high workload suggest this method may be inappropriate for the recapture of escapees. KEY WORDS: Atlantic cod · Fish escape · Aquaculture · Telemetry · Recapture Full text in pdf format PreviousNextCite this article as: Serra-Llinares RM, Nilsen R, Uglem I, Arechavala-Lopez P, Bjørn PA, Noble C (2013) Post-escape dispersal of juvenile Atlantic cod Gadus morhua from Norwegian fish farms and their potential for recapture. Aquacult Environ Interact 3:107-116. https://doi.org/10.3354/aei00051 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 3, No. 2. Online publication date: January 30, 2013 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2013 Inter-Research.

REGULAR ARTICLES / ARTICLES RÉGULIERSSize-related predation reduces intramorph competition in paedomorphic Alpine newts

Evolutionary theory assumes that facultative paedomorphosis in newts and salamanders is adaptive in allowing either a younger age at maturity or resource partitioning between the heterochronic morphs. In newt populations that only take the metamorphic ontogenetic pathway, juveniles are terrestrial and avoid food competition with larvae and breeding adults. In contrast, in populations where paedomorphosis occurs, branchiate newts of all sizes coexist in the aquatic habitats, posing the question of whether intramorph competition exists and its relationship with the evolution of paedomorphosis. We studied size-related predation in such a size-structured community of branchiate Alpine newts (Triturus alpestris) inhabiting a deep alpine lake. Although gape limitation may explain such size-related predation, individuals also exhibited selectivity according to prey size. Amongst small prey that were within the capture range of all newt size classes, smaller newts preyed on smaller items than did larger ones. We assume that such decisions favour the coexistence of different-sized individuals. It is suspected that such size-selective predation on items which are avoided by water-living metamorphs allows the maintenance of facultative paedomorphosis, in favouring resource partitioning between morphs.

&lt;b&gt;REGULAR ARTICLES / ARTICLES RÉGULIERS&lt;/b&gt;&lt;p&gt;Size-related predation reduces intramorph competition in paedomorphic Alpine newts

Evolutionary theory assumes that facultative paedomorphosis in newts and salamanders is adaptive in allow- ing either a younger age at maturity or resource partitioning between the heterochronic morphs. In newt populations that only take the metamorphic ontogenetic pathway, juveniles are terrestrial and avoid food competition with larvae and breeding adults. In contrast, in populations where paedomorphosis occurs, branchiate newts of all sizes coexist in the aquatic habitats, posing the question of whether intramorph competition exists and its relationship with the evolution of paedomorphosis. We studied size-related predation in such a size-structured community of branchiate Alpine newts (Triturus alpestris) inhabiting a deep alpine lake. Although gape limitation may explain such size-related predation, indi - viduals also exhibited selectivity according to prey size. Amongst small prey that were within the capture range of all newt size classes, smaller newts preyed on smaller items than did larger ones. We assume that such decisions favour the coexistence of different-sized individuals. It is suspected that such size-selective predation on items which are avoided by water-living metamorphs allows the maintenance of facultative paedomorphosis, in favouring resource parti- tioning between morphs. 948 Resume : Chez les tritons et les salamandres, les theories evolutives considerent que la pedomorphose facultative est adaptative en permettant l'acquisition precoce de la maturite sexuelle ou le partage des ressources entre les formes

Ontogenetic changes in the diet of the coral reef grouper Plectropomus leopardus (Serranidae):patterns in taxa, size and habitat of prey

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 180:233-246 (1999) - doi:10.3354/meps180233 Ontogenetic changes in the diet of the coral reef grouper Plectropomus leopardus (Serranidae): patterns in taxa, size and habitat of prey Jill St John* Department of Marine Biology, James Cook University, Townsville 4811, Australia *Present address: Ishigaki Tropical Station, Seikai National Fisheries Research Institute, 148-446, Fukai-Ohta, Ishigaki-shi, Okinawa 907-0451, Japan. E-mail: jstjohn@snf-its.affrc.go.jp ABSTRACT: Stomach contents and diet of a wide range of sizes (4.7 to 57.3 cm standard length [SL]) of the predatory coral trout Plectropomus leopardus (Fam. Serranidae) collected mostly from the northern Great Barrier Reef during the summers of 1991 and 1992 were examined. Overall, 422 prey in 28 families of fishes were identified of which 3 families, Clupeidae, Pomacentridae and Labridae, represented more than 60% of the diet. Average daily consumption of prey in P. leopardus was 2.8% of relative body weight and fish of 20 to 49.9 mm SL were eaten by all size classes. Juvenile (up to 20 cm SL) and adult P. leopardus have distinct diets. The major dietary shift in the type, species composition, length and shape of prey occurs at approximately 20 cm SL, just prior to the onset of maturity. Juveniles consumed a high proportion of benthic dwelling crustaceans, mostly penaeid shrimps, whereas adults were almost entirely piscivorous. The number of families of fishes in the diet did not increase with the size of predator as some families were eaten exclusively by juveniles or adults. Abundances of fish families in the diet varied ontogenetically and among size classes in small adults. Predation was related to size of prey in juvenile and small adults. Up to 35 cm SL, the range of prey sizes widened with increases in predator length, as larger fish ate larger prey, concomitantly feeding on small fishes, especially schooling species. However, the composition of the diet and length of fish prey did not change in P. leopardus after 35 cm SL and prey did not deepen after 45 cm SL. Body depth of prey was more important than length in size-related feeding on 2 common families of fishes with different shapes. In general, larger P. leopardus appeared to feed optimally on deep-bodied fish, whereas juveniles avoided gape limitation by consuming more slender fish. All size-related predation in P. leopardus, however, was easily decoupled by the presence of highly abundant small fishes in large visible schools. KEY WORDS: Feeding ecology · Coral reef fish · Serranidae · Dietary analyses · Size-related predation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 180. Publication date: May 03, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Development of a Foraging Model for a Field Population of the South American Sun-Star Heliaster helianthus

SUMMARY (1) The objective of this study is to examine analytically size-related predation in a population of Heliaster helianthus in an intertidal rocky shore habitat in central Peru. Among 11243 prey individuals recovered from a total of 1132 feeding predators, the mussel Semimytilus algosus was predominant with an average proportion of 85-5% and 85-7% by number and biomass, respectively. (2) A graph describing the patterns of energy/biomass distribution among different size-classes of mussel prey in the field was obtained and used for comparison with the patterns of prey-size utilization by the predator population. Larger individuals of H. helianthus fed on clumps of Semimytilus algosus containing larger mussels, but the biomass distribution of all S. algosus consumed closely resembled that of the natural prey population, except in the smallest predator size-group (< 109 cm) where small mussels were more strongly represented in the diet. (3) A model was developed to account for the selection of meal sizes in the H. helianthus population. Frequency distributions of observed meal sizes for four predator size categories were compared and the patterns observed were generally in agreement with the model. (4) The study suggests that 'energy maximization', the core assumption of classic optimal diet choice models, is not relevant to the choice of prey size and meal size in H. helianthus. Difficulties in applying optimal foraging models based on the energy maximization premise to the analysis of foraging patterns in field animal populations are discussed.

Perch (Perca fluviatilis) and Pike (Esox lucius) in Windermere from 1940 to 1985; Studies in Population Dynamics

The aduit population of perch (Perca fluviatilis) in Windermere was severely reduced by an experimental trap fishery from 1941 to 1947 in one basin and from 1941 to 1964 in the other and has been monitored since. A gillnet fishery for pike (Esox lucius) &gt;550 mm began in 1944 and has continued since. Changes in numbers, recruitment, mortality, growth, biomass, and fecundity have been measured. Summer water temperature and population density affected perch growth; temperature affected pike growth from 1944 to 1959, but not thereafter. A model involving correlations with temperature and negative correlations with abundance of adult perch and 0 group pike explained 90% of variation in perch recruitment for part of the period. Pike recruitment was correlated with temperature. In perch adult mortality rate and growth rate are correlated. Perch numbers are recovering after a 98% adult mortality from disease in 1976. Temperature and size-related predation within and between the two species appear to be the main controlling factors, but the relationships have changed from one part of the period to another.

Variations in the sizes of gonads, eggs and larvae of the dace, Leuciscus leuciscus

Prespawning female dace were examined in 7 successive years; in 6 years mean egg size (mm3) and egg number were inversely related and hence the ovary weights of equivalent-sized females were constant. Fecundity increased logarithmically with fish length, and an index of reproductive effort (ovary weight ÷ length cubed) also increased. The number of eggs per gram of ovarian tissue decreased with fish length; this was because mean egg size (mm3) increased and not because of a change in the proportion of connective tissue in the ovary. But in 1977, both egg number and mean egg size were low, although very high somatic growth had occurred in the previous, very warm, summer of 1976. Eggs from different-sized female dace were artificially fertilized, and incubated at a constant temperature. Dry weights of larvae, egg dry weights, mean egg size and larval starvation times showed linear correlations with each other and with parental (female) lengths. The progeny from the very smallest parent died several days earlier than those from the other parents. Size-related predation rates may be of more consequence than starvation death in natural populations. The optimum position of dace along the continuum between many small eggs and fewer larger eggs may vary at different levels of reproductive effort.

Burst Swimming and Size-Related Predation of Newly Emerged Coho Salmon Oncorhynchus kisutch

Abstract Burst swimming by newly emerged coho salmon from two populations was studied with electrical shock stimulation and high-speed cinematography. At emergence, Morrison Creek fish were larger (31 versus 27 mm standard length) than fish from Wade Creek. The larger fish attained greater mean and maximum burst speeds than the smaller fish and differences in swimming performance (up to 80%) were greatest over the first 0.03 s of acceleration. When exposed to 140-mm coho salmon predators, more of the larger Morrison Creek fish survived than of the Wade Creek fish. Size-mediated differences in burst swimming performance appear to be the basis for the observed difference in susceptibility to predation.

Winter feeding by asteroids on a subtidal sandbed in British Columbia

Abstract The winter feeding of the asteroids Mediaster aequalis, Luidia foliolata, Pisaster brevispinus and Pycnopodia helianthoides on a subtidal sandbed in British Columbia is reported. Bivalve predation and experiments with the latter three species examining size-related predation, sand as a prey refuge and prey escape behavior are reported using the cockle Clinocardium nuttallii. M. aequalis is a small species with a very broad diet and mainly a microphagous feeder which may graze recently settled bivalve larvae. L. foliolata is a burrowing species which specializes in swallowing small infaunal bivalves whose size usually cannot exceed its disc (mouth) diameter of 40 mm. P. brevispinus is large and grazes barnacles on hard substrates, and on sand specializes in excavation of larger bivalves such as the geoduck clam Panope abrupta and the jacknife clam Solen sicarius. P. helianthoides is a large, highly opportunistic predator which grazes epifauna on hard substrates, excavates larger bivalves from sand...