Graduation date: 1984

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Wound healing and recovery from injury were investigated in eggs and larvae of herring (Clupea harengus L.), plaice (Pleuronectes platessa L.) and salmon (Salmo salar L.). The resistance of herring eggs to mecha.nical damage was first examined. The chorion of eggs before and just after fertilisation could be burst by loads of 4-30 g but eggs 5 h post-fertilisation could withstand over 1000 g without bursting. Resistance remained high until just before hatching when it decreased to 20-680 g. The vitelline membrane, however, showed a lower resistance at all stages. Early herring and plaice larvae were caught and eaten by medusae (Aurelia aurita, Tiaropsis multiserrata, Bougainvillea sp.), hydroids (Sarsia sp.), megalopa larvae of the prawn Nephrops norvegicus and adult mysids. Early herring larvae survived minor stings from an Aurelia ephyra, and also experimentally inflicted lesions such as superficial scratches, suction wounds and amputation of up to 2 mm of the tail in sea water. The caudal region of the primordial fin regenerated within a month when less than 1 mm was cut off. Yoll, sac and first feeding herring also survived an incision of 0.3 mm long through the body ventral to the notochord and dorsal to the gut; in starving larvae survival was poorer in the later stages of starvation. When skin was removed in larvae of all 3 species the mortality depended on the area of the lesion, thp maximum area tolerated increasing with larval size. In sea water the threshold area was 0.1-0.2 mm2 dO.r 6-8 mm long plaice, <: 0.3 mm for 10-13 mm long herring and 0.3-0.4 mm for 14-17 mm long herring. In river water the threshold was 1~2mm for 19':1l2m1m long saImon and 6.5-8 mm for 26-28 mm long salmon. The thresholds w ore about 1-3% of the total body surface area. Tolerance was increased in isosmotic salinities, the threshold area being as high as 10-14% of the body surface in 24-28 mm long salmon in 8%0. Healing of skin lesions was observed in vivo and by histology, the main response being a mass migration of epidermal cells from the periphery of the lesion. Wound areas of 0.1-7 mm closed in 4-12 h, the mean rates of cell migration being 40-110JUm/h at 10_11°C. The rate of migration was temperature dependent. The normal skin structure was restored with regeneration of a new basement membrane and dermis within 3 weeks. Older stage larvae showed an inflammatory response similar to adult fish.

Nutritional aspects of three species of marine fish larvae, herring Clupea harengus L., plaice Pleuronectes platessa L. and turbot, Scophthalmus maximus L. were examined. Larvae were fed three different diets all of which were derived from rotifers Brachionus plicatilis (O.F. Mtlller). These rotifers had been mass cultivated on baker's yeast and then enriched with baker's yeast, or with one of two unicellular algae, Isochrysis galbana Park or Nannochloropsis (Nannochloris) oculata (Droop) Hibberd. The biochemical changes that these enrichments conferred on the rotifer were examined. There was little difference in proximate and amino acid compositions. Dry weights, and calorific contents of the rotifers fluctuated according to the type, temperature and duration of enrichment, with the yeast enriched rotifers tending to weigh less (200-320 ng) than their algal counterparts (250-370ng). Major differences were found in the total fatty acid profiles of the rotifers. Yeast-enriched rotifers had no 18:3n-3 or 20:5n-3 and only trace amounts of 22:6n-3 fatty acids. The Nanrinochioropsis-enriched rotifers had substantial amounts of n-3 fatty acids though only of 20:5n-3 (11-14%), while rotifers enriched with Isochrysis had only trace amounts of 20:5n-3 (2-4%). All three species of fish responded similarly to the yeast enriched rotifer diet. Their growth, in terms of length and weight, was minimal and they never developed any fin ray elements. Both flatfishes developed a looped gut in the short growth duration on this diet and some turbot (20%) inflated their swim bladder. This retardation of growth was attributed to the lack of long chain highly unsaturated n-3 fatty acids (n-3 HUFA) in the diet. During one month feeding trials it was shown that herring and plaice were able to exploit both algal-enriched rotifer diets equally well. Turbot, on the other hand grew better, over 14 days, on rotifers enriched with lsochrysis compared with Nannochioropsis. The reaction of the different species was linked to the fatty acid profiles of the diet. Hence, turbot require a dietary input of 22:6n-3 while herring and plaice thrived equally well on diets containing only 20:n-3. Juvenile plaice consistently exhibited improved pigmentation when Isochrysis compared to Nannochloropsis were used as the rotifer enrichment. The effect was attributed to specific nutrients particular to algal chloroplasts, which need to be present in the diet of the larvae up to metamorphosis. Assessment of daily rations, employing the rotifer enriched with Isochrysis diet only, showed herring to reduce their food intake from 46 to 19% body dry weight/d between days 10-21 post hatch while turbot consumed between 34-169% body dry weight/d with no apparent age related effects. The gross growth efficiencies (Ki, Brett &amp; Groves, 1979) for both species were seemingly unaffected by age related processes and fluctuated between 15-50% in turbot and 20-61% in herring according to fluctuations in daily food intake. Ingestion is further described for both species with a linear model that related food intake to larval weight. The weight-specific ingestion was found to be a constant 13% and 43% of body dry weight in herring and turbot respectively. The weight-specific ingestion and specific growth rate estimates were combined with other data available from the literature, revealing that larvae tend to consume food (in dry weight) at a level equivalent to approximately twice their daily dry weight increase.

My research has focused on the identification, assemblage dynamics, and horizontal distribution patterns of larval fishes around rocky reefs in the Gulf of California, Mexico. In Chapter One, I analyze a series of light-trap collections taken over 35 nights at San Carlos, Sonora. Nearly 14,000 larvae from 19 families were collected. The five most abundant families contributed 90% of the larvae and the top ten families contributed 99%. Larvae of non-pelagic spawners (gobiids, labrisomids, tripterygiids, chaenopsids, pomacentrids, and bythitids) dominated the collections. Larval catches ranged from 7.5 to 2330.3 larvae/45 min, but changes in catch rate were not related to changes in ambient moonlight. In contrast, the volume of zooplankton collected was correlated with moonlight intensity. Dynamics of the ten dominant fish families were highly variable, but in most cases a large proportion of the larvae were caught on just a few nights. Taxonomic and size selectivities were apparently less severe in my study than in previous Australian studies, and the use of light-traps should be explored further. In Chapter Two, I outline the prediction that larvae of small, non-pelagic spawning fishes should more frequently be retained over reefs during development than fishes with other combinations of body size and egg type, and I describe my research testing this prediction. I made about 160 collections of fish larvae with a light-trap and plankton net at 1, 20, and 100 m from rocky shorelines. These collections yielded 27,265 larvae from about 50 families. Based on larval size frequencies, near-reef concentration gradients, and abundances offshore, I identified four families that can complete development over the reef but also have larvae dispersed offshore (Clupeidae, Engraulididae, Gerreidae, and Haemulidae). In addition, I identified seven families that primarily develop over reefs and have few or no larvae dispersed offshore (Tripterygiidae, Chaenopsidae, some Labrisomidae, Dactyloscopidae, some Gobiidae, Gobiesocidae, and Bythitidae). Adults of these seven families are mostly small, non-pelagic spawners. Larvae from four taxa of larger non-pelagic spawners (Ophioblennius, Labrisomus, Balistes, and Pomacentridae) did not appear to develop over reefs. These findings are in accord with the prediction I made. Chapter Three is a preliminary guide to identification of Gulf of California blennioid larvae. Although blennioid larvae are poorly known and few species have been described, they are well represented (ca. 20,000 larvae from five families) in my collections taken near reefs in the Gulf. Illustrations of 20 species, and brief descriptions of key characters for these and several additional species, are provided. More detailed taxonomic studies on Gulf blenniid, dactyloscopid, tripterygiid, labrisomid, and chaenopsid larvae are in progress.

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Environmental control of interactions between larval fish and their prey, and the potential influence of this relationship on fish feeding and recruitment, were assessed using empirical models developed using data drawn from the literature and developed in field studies. Ingestion rates of larval fish in laboratory and natural environments were found to differ in relation to food density. In laboratory studies, larvae show a strong functional response to prey density. Larvae situated in situ consume food at much higher races than would be predicted from laboratory studies and these rates are independent of prey density at known in situ densities. This discrepancy between laboratory and field feeding rate-food density relationships can be partly explained by the in situ contribution of small-scale turbulence to predator-prey encounter rates. Field studies of the influence of wind on nearshore hydrography showed that wind-induced upwelling generated favorable combinations of nutrients, light, and small-scale turbulence for production by phyto- and zooplankton. The distribution of microplankton $(<$80 $ mu$m) that resulted from these upwelling episodes was quantitatively described by the cumulative longshore wind velocity during the summer months. Microplankton abundance was greatest within 4 km of a major spawning site for capelin, Mallotus villosus, an economically and ecologically important forage species in the north Atlantic Ocean. Interannual variability in the intensity and frequency of upwelling-favorable winds was positively and significantly correlated with recruitment levels in the NAFO 2J3K capelin population. A new recruitment forecasting model, using an upwelling-related wind index as an input, explained more of the variance in capelin recruitment than did a previously published model. These results suggest that larval capelin are more likely to be food-limited in years when wind conditions are unfavorable for upwelling, and that recruitment in this fi

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