José P. Andrade

Growth and survival of cuttlefish (Sepia officinalis) of different ages fed crustaceans and fish. Effects of frozen and live prey

Abstract Three feeding experiments, using live mysid shrimp, grass shrimp or fish fry as prey for 1-, 30- and 60-day-old cuttlefish were conducted to determine the efficiency of each dietary source in relation to cuttlefish size and age. Additionally, a fourth experiment using fish fry and grass shrimp, but previously frozen, was also conducted. The results showed that when 1-day-old cuttlefish were fed mysids, grass shrimp or fish for 4 weeks, mysids were the best prey, but only during the first week. From this moment until the end of the experiment, the best growth rate was when cuttlefish were fed grass shrimp. Cuttlefish fed fish fry showed the poorest growth rate throughout the experiment. Similarly, cuttlefish aged 30 or 60 days fed grass shrimp or fish fry had the best growth rates when fed grass shrimp. When cuttlefish were fed live fish, survival increased with size of cuttlefish (73.3%, 91.7% and 100% for 1, 30 and 60 days cuttlefish, respectively). In the fourth experiment, using frozen diets, overall acceptance of each diet (feeding rates) was the same for fish and shrimp. However, lower growth was obtained when cuttlefish were fed fish compared to grass shrimp. This lower growth was due to a lower food conversion (28% vs. 41%). Since cephalopod paralarvae and juvenile most likely need prey rich in polyunsaturated fatty acids (PUFA), phospholipids and cholesterol, and a moderate content in neutral lipids, we have analyzed the biochemical compositions of the different prey to evaluate the influence of this factor on growth and survival.

Morphological study of Diplodus sargus, Diplodus puntazzo, and Lithognathus mormyrus (Sparidae) in the Eastern Atlantic and Mediterranean Sea

Truss morphometric measurements were made on white seabream, Diplodus sargus, sharpsnout seabream, Diplodus puntazzo, and striped seabream, Lithognathus mormyrus from Portugal, Spain, Italy and Greece. Univariate and multivariate statistical analyses were used to discriminate populations. Stepwise discriminant analysis yielded a reduced variable set that identified significant differences between all the four countries. The overall percent-correct classification rate for the four samples from the stepwise discriminant analysis based on 7, 9 and 10 adjusted morphometric characters (D. sargus, D. puntazzo, L. mormyrus samples, respectively), was 93.7, 90.6 and 96.3%. For each species, there was a significant degree of morphological dissimilarity between countries. A clear geographical gradient occurs between the Atlantic and the Mediterranean samples, suggesting that in some cases the fish from these areas represent separate groups.

Effects of culture density and live prey on growth and survival of juvenile cuttlefish, Sepia officinalis

The effects of culture density on growth and survival of juvenile cuttlefish were tested. Groups of 1, 3 and 5 hatchlings were placed in small containers with bottom surface of 80 cm2, obtaining individual densities of 125, 375 and 625 cuttlefish m−2, respectively. Additionally, groups of 5 hatchlings were placed in containers with 2 different bottom areas (80 and 240 cm2), providing culture densities of 625 and 42 cuttlefish m−2, respectively. A total of 120 hatchlings were used and experiments lasted for 40 days. No differences were found in growth between any of the densities tested throughout the experiment until 35 days old. After this, cuttlefish placed in isolation grew significantly larger. A second experiment was conducted in a flow through system, using two rectangular tanks with bottom surface of 0.5 m2. Two groups of 25 cuttlefish hatchlings were used in this experiment, which lasted for 40 days. Both groups were fed live juvenile shrimp (Crangon crangon) during the first 5 days. Afterwards, one group was fed live fish fry of different species, while the other continued to be fed shrimp. After day 10 and until the end of the experiment, hatchlings fed shrimp grew significantly larger than those fed fish fry. Survival of hatchlings fed shrimp or fish fry after 40 days was of 100% and 68%, respectively. Total protein content of both prey types was similar. Therefore, the higher polar lipid content, especially due to the higher phosphatidylcholine and phosphatidylethanolamine levels observed in the shrimp, compared to fish fry could possibly be one of the major factor to explain the significantly higher growth rates for S. officinalis juveniles fed shrimp. Also, the percentage of polar lipids in the shrimp (47.4%) was closer to the one of juvenile cuttlefish (38.1%) than the composition of polar lipids in fish fry (10.4%). This could also be an important factor to explain the poor growth and survival obtained when feeding fish fry to the cuttlefish.

The effects of temperature in the life cycle of two consecutive generations of the cuttlefish Sepia officinalis (Linnaeus, 1758), cultured in the Algarve (South Portugal)

We are presently culturing the 4th generation of thecuttlefish, Sepia officinalis in our laboratory. A firstgeneration (F1) was grown from eggs collected from the wild (Ria Formosa–South Portugal) during the summer, at mean temperatures of 27°C ± 3°. In the present study, a second generation(F2), originated from eggs laid in the laboratory by females from F1 wascultured between the start of autumn and the end of spring, at meantemperaturesof 15 °C ± 4 °C. The life cycle ofcuttlefish from F2 was compared to F1. Populations of 30 cuttlefish were usedineach experiment. Cuttlefish were grown from one day old until the cycle wascompleted (when the last female in each population had died). Cuttlefish fromF2cultured at much lower temperatures had a longer life cycle, of almost 9 months(260 days) compared to cuttlefish from F1, which completed their cycle in lessthan 6 months (165 days). Cuttlefish from F2 grew significantly larger (U =0.00; p < 0.01) with mean weights of 343.3 ± 80.5 g and248 ± 33.1 g for males and females, respectively, comparedtoF1 (199.6 ± 40 g and 143.3 ± 30.9 g formales and females, respectively). Females from F2 had higher fecundity (225eggsfemale−1) compared to females from F1 (144 eggs perfemale−1), produced bigger eggs (t = 45.60752; p < 0.0001),weighing 0.74 ± 0.18 g, compared to 0.46 ± 0.11 fromF1,and bigger hatchlings (t = 7,144783; p < 0.0001), weighing 0.10 ±0.02g, compared to 0.09 ± 0.02 g for the summerpopulation.

Status of the Guadiana Estuary (south Portugal) during 1996-1998: An ecohydrological approach

The aims of this study were to monitor basic hydrological and ecological characteristics of the Guadiana Estuary (1996-1998) before the construction of the Alqueva dam. This work was carried out to determine how environmental factors affect seasonal and tidal variations of plankton populations in the estuary. The available information on the subcatchment of the estuary (e.g., urban, agricultural and forested areas) was integrated into a geographic information system-based software program. Mean monthly river flow varied markedly on a seasonal and yearly basis. River flow near Mértola (ca 50 km upstream from the mouth) reached 3400 2 10 6 m 3 in winter and decreased to 42 2 10 6 m 3 in summer. With respect to nutrients, nitrogen to phosphorus ratios indicated some limitation by phosphorus, except at the end of summer, when nitrogen limitation appeared. During this period, cyanobacterial blooms usually occurred in the upper/middle estuary. Estuarine Turbidity Maximum may significantly influence the retention of zooplankton in the estuary. The fish larval life cycle, especially sensitive to environmental alterations, showed high ratios of ribonucleic to desoxyribonucleic acids indicating good physiological condition. It was concluded that an ecohydrological approach, allowing integration of different elements from the cellular to the habitat level into a geographic information system, can contribute to a better understanding of the processes that influence the aquatic biota of the estuary. The approach will be a useful assessment tool for monitoring the estuary following dam completion.

The use of Artemia sp. or mysids as food source for hatchlings of the cuttlefish (Sepia officinalis L.); effects on growth and survival throughout the life cycle

Twoexperiments were conducted to determine the effects ofArtemia sp. or mysids on growth and survival ofS. officinalis hatchlings, and their effect throughout thelife cycle. For experiment I, for the first 20 days, one group was fed adultArtemia sp. and the other was fed mysid shrimp(Paramysis nouvelli). Eggs laid by females in both groupswere counted and weighed, and hatchlings were weighed, to determine differencesin both groups. For experiment II, during the first 10 days, one group was fedArtemia sp. and the other was fed mysids (P.nouveli). After the period of differentiated feeding, the 2 groupsinexperiment I were fed grass shrimp (Paleomonetes varians)to 70 days old, and dead crabs (Carcinus maenas)afterwards. Cuttlefish in experiment II were fed grass shrimp from day 10 untilthe end of the experiment. For both experiments, hatchlings fed mysids grewsignificantly bigger (p < 0.01) and survival was higher. For experiment I,eggs laid by females fed mysids and the hatchlings born from these eggs werebigger (p < 0.001) compared to the group fed Artemiasp.initially. Individual fecundity was slightly higher for females in the groupfedArtemia sp. (163 eggs female−1) than forthe group fed mysids (144 eggs female−1). Egg laying startedatthe age of 125 days and lasted 45 days in both groups. Time between first egglaying day and first hatchlings to be born was 21 days. The last female to die(after spawning) in both groups was 167 days (less than 6 months old).

Effects of feeding live or frozen prey on growth, survival and the life cycle of the cuttlefish, Sepia officinalis (Linnaeus, 1758)

The effects of feeding live or frozen grass shrimp (Palaemonetes varians) to the cuttlefish, Sepia officinalis, were determined in two experiments. During Experiment I, two populations of 30 cuttlefish (aged 90 days old) were fed either live or frozen grass shrimp. Cuttlefish fed live shrimp grew larger, matured earlier, had a shorter life cycle (255 days) than the ones fed frozen shrimp (282 days), and had lower mortality. Females from the group fed frozen shrimp matured a month later but were significantly larger, 130.9 ± 38.5 g, compared to 74.2 ± 16.0 g, laid larger eggs, 0.47 ± 0.11 g, compared to 0.28 ± 0.10 g, and had higher individual fecundity (411 eggs female−1, compared to 150 eggs female−1). Newly born hatchlings from both groups had similar weights. During Experiment II, six replicates of 15 cuttlefish (50 days old) were used, three for each of the two diets tested. The exact same amount of live or frozen shrimp was provided to both populations twice a day. No differences in growth and feeding rates or food conversions were found at the end of the experiment. During the first week, cuttlefish fed frozen shrimp grew larger, and had higher conversion rates, compared to the ones fed live shrimp. Mortality was higher for the group fed live shrimp (36.6%) in Experiment II, mainly occurring during the last week. Mortality for cuttlefish fed frozen shrimp in Experiment II was 2.2%. Results obtained here indicate that freezing the grass shrimp only had a negative effect on the survival of S. officinalis in Experiment I.

A comparative study of the diet of Loligo vulgaris (Lamarck, 1799) (Mollusca: Cephalopoda) from the south coast of Portugal and the Saharan Bank (Central-East Atlantic).

Abstract This paper presents data on the diet of the squid, Loligo vulgaris (Lamarck, 1799) from the south coast of Portugal (Algarve) and from the Saharan Bank (Central-East Atlantic). A total of 964 squid was collected from the Algarve coast, between March 1993 and October 1994, from bottom trawling. An additional sample of 70 stomachs was obtained in the Algarve coast from the hand jigging fishery during 1991 and 1992. In the Saharan Bank, 848 squid were obtained, between June 1993 and January 1994, with bottom trawling. Stomachs with contents for trawled squid from the Algarve coast, and the Saharan Bank represented 28.1% and 40.8%, respectively. Fish was always the main component of the diet in both regions, representing 88.6% of the total weight of the prey found in the stomachs, for the Algarve coast, and 70.9% for the Saharan Bank. The occurrence percentage and the percentage in number indicated that Trachurus trachurus and fish belonging to the family Gobiidae were the most frequent fish found in the Algarve samples, while flatfish were the most common fish in the Saharan Bank samples. Loligo vulgaris was the dominant cephalopod found in the stomachs for both regions. No differences in the diet were found between males and females. The comparison between immature and mature squid showed that the importance of fish was higher in mature squid, for both regions. The squid captured from the Algarve coast by bottom trawling (at greater depths and offshore) fed primarily on fish, while those captured with hand jigging (inshore, at lower depths) contained an important percentage of crustaceans.

The influence of culture density and enriched environments on the first stage culture of young cuttlefish, Sepia officinalis (Linnaeus, 1758)

The culture of Sepia officinalis hatchlings and juveniles at different densities and enriched environments was investigated. Experiments were conducted to determine effects of culture density and the use of a substrate on growth and survival. Experiment I studied the effect of three different densities (52, 515 and 1544 hatchlings m−2). Experiment II tested the effects of the enriched environment, using a sandy bottom with pvc shelters. Experiment III tested the effects of density on growth, survival, feeding rates and food conversions. Cuttlefish were fed live grass shrimp at rates of 20% body weight per day (BW d−1). Grass shrimp (Palaemonetes varians) was supplied ad libitum as food in all experiments. In experiment I, growth was different between the three densities, with highest growth for density of 515 hatchlings m−2. IGR was of 8.8, 9.6 and 9.2% BW d−1 for the three densities tested, respectively. Both groups of experiment II had similar growth. IGR was of 10.1 and 9.7% BW d−1 for enriched and non-enriched environments, respectively. Densities of 10, 45 and 120 juvenile m−2 were used in experiment III. Significant differences in feeding rates were only found between densities of 10 and 120 cuttlefish m−2 during the last week. Results indicate that culture of cuttlefish hatchlings could be done in a non-enriched environment, with densities not exceeding 500 hatchlings m−2 and minimum bottom areas of about 600 cm2. Densities of 120 juveniles m−2 in a minimum area of about 1083 cm2 should be considered for juveniles between 5 and 25 g.

Comparison of RNA/DNA ratios obtained with two methods for nucleic acid quantification in gobiid larvae

In this paper, RNA and DNA contents and RNA/DNA ratios obtained with two fluorometric methods for the extraction and quantification of nucleic acids in individual estuarine gobiid larvae are compared. A total of 141 gobiid larvae, collected in the Mira and Guadiana estuaries (Portugal), were analysed. This study indicated that the nucleic acids content and RNA/DNA ratios of individual larvae varied with the procedure used. The two methods yielded similar log DNA values but different log RNA and log (RNA/DNA). The differences could be due to a number of factors related to specific steps of tested protocols. Comparison of nucleic acids contents and calibration of the two methods by regression analysis provided a reasonable basis for comparison although differences between estimates were evident.