Population biology of grey gurnard (Eutrigla gurnardus (L.); Triglidae) in the coastal waters of Northwest Wales

The grey gurnard Eutrigla gurnardus (L.) has been identified by ICES as a potential commercial species in the NE Atlantic with recommendations made to derive information on population biology for stock assessment purposes. However, data on the population biology of this species is limited. In this study, data on the age, growth and maturity of grey gurnard were collected by otter trawling in the coastal waters of northwest Wales and Eastern Anglesey. Total length (TL) of fish sampled ranged between 2.1–33.0 cm (male) and 1.9–36.9 cm (female) with the majority of female (70.8%) fish between 11 and 20 cm TL and male fish (70.5%) between 11 and 18 cm TL. The percentage of fish >20 cm TL was larger for females (30.4%) compared to males (17.6%). Total weight (TW) for female and male grey gurnard in the stratified subsample ranged from 1.9 to 499.9 g for females and 2.1–390.0 g for males, with the majority of female (66.3%) and male (76.1%) fish between 10 and 60 g. TL/TW relations for male and female fish and both sexes combined were: TW = 0.006TL^3.07, TW = 0.007TL^3.03 and TW = 0.007TL^3.05 respectively. Age structure (based on otolith reading) ranged between 0.5 and 7.5 years old for females and 0.5 to 5.5 years old for male with the majority of female (41.7%) and male (46.0%) fish aged as 1.5 years old. The age structure of female and male grey gurnards was significantly different with the majority of older fish (>2.5 years) being female. The von Bertalanffy growth functions were calculated as L_t = 32.4[1 ? e^{?0.24(t + 1.41)}] for males, L_t = 45.9[1 ? e^{?0.16(t + 1.37)}] for females and L_t = 44.0[1 ? e^{?0.18(t + 1.20)}] for both sexes combined. Instantaneous rates of total mortality were similar for males and females and the combined Z value 1.00 year^?1 with the natural mortality rate estimated as 0.33 year^?1. The size at 50% maturity (L₅₀) was estimated to be 25.3 cm TL for males, females and for both sexes combined. Age at 50% maturity (A₅₀) was 3.2 years for both males and females. The results of this study provide the first information on the population biology of E. gurnardus in the Irish Sea, the first detailed study in the NE Atlantic since 1985 and helps to address the data gap identified by ICES in knowledge of the population biology of this species.     

Feeding habits of red gurnard,Aspitrigla cuculus (L. 1758) (Scorpaeniformes,Triglidae), along the Catalan coast (northwestern Mediterranean)

Stomach contents of 193 specimens of the fish Aspitrigla cuculus (collected at quarterly intervals) are analyzed to determine diet, and variations in diet according to size and season. Crustaceans (% No = 93 %, % Weight = 63 %) and teleostean fish (% N = 6 %, % W = 30 %) constitute the basic food. Feeding habits change at c. 85 mm and again at c. 140 mm (size of sexual maturity) total length. The importance of nycthemeral migrators decreases with size, while the circalitoral benthos increase inversely. In adults, the seasonal variations show only substitutions between benthic prey types.     

Tracing the life history of red gurnard (Aspitrigla cuculus) using validated otolith annual rings

Back calculation, marginal increment analysis and modal progression analysis were used to trace growth processes of the red gurnard, Aspitrigla cuculus L., in the Mediterranean Sea. Three false rings appeared regularly on otoliths and were hypothesized to refer to the ontogeny on the basis of the study of the recruitment and reproduction processes of the species. The first two rings were laid down during the first pelagic period and the transformation to the bottom mode of life, respectively. The third ring corresponded to the first spawning at the end of the second year of life. The marginal increment analysis demonstrated that one opaque and one translucent zone is formed each year, the translucent ring corresponding to the period of slow growth in the winter. Temperature and salinity of Mediterranean waters below the thermocline where red gurnard live do not undergo seasonal variations. Therefore, traditional interpretation of the discontinuity patterns on otoliths related to the decrease of water temperature should be rejected for Mediterranean fish distributed on the deep shelf and slope. Discontinuities in otolith structure may be related to seasonal variation in feeding intensity as a consequence of decreases in the benthic mysids biomass and time available to find food due to reduced daylight. Future research should focus on the trophic ecology of the demersal fishes and the seasonal fluctuations of the prey resources during the year in order to assess the role of the food supply with regard to otolith growth patterns in the Mediterranean Sea.     

Age,growth and maturity of tub gurnard (Chelidonichthys lucerna Linnaeus 1758; Triglidae) in the inshore coastal waters of Northwest Wales,UK

The tub gurnard Chelidonichthys lucerna has been identified by ICES as a potential commercial species in the northeast Atlantic with recommendations made to monitor landings and discards and to derive information on population biology for stock assessment purposes, however, data are lacking for the species in the northeast Atlantic. Therefore, aims of this study were to provide data on the size/age‐structure and patterns of growth, maturity and mortality of C. lucerna in Northwest Wales, UK, and in doing so to provide data on the biological characteristics of the most northerly population studied to date for comparison with the existing data for southerly Mediterranean populations. Data on the age, growth and maturity of C. lucerna were collected by otter trawling (73 mm cod‐end stretched mesh size) in the coastal waters of Northwest Wales, UK in October (2000–2011, excluding 2006). Total length (TL) of fish sampled ranged between 10.5–41.0 cm (males) and 10.4–57.5 cm (females). The majority of the female fish were between 20–30 cm TL (60.2%) and the majority of the male fish between 20–30 cm TL (58.3%) respectively. TL/weight (W) relations for male and female fish were similar and the combined data was described by W = 0.0067 TL^3.10. Age of fish ranged between 1–7 years old for female fish and 1–5 years old for male fish respectively with the majority of female fish 3 years old (40%) and the majority of male fish 3 years old (37%). The age structures of female and male tub gurnards were not significantly different with the older age classes consisting predominantly of female fish. Both males and females exhibited similar asymptotic growth patterns and the combined von Bertalanffy growth function was TL_t = 51.6 (1 ? e ^{[?0.25(t + 0.41)]}). Instantaneous rates of total mortality were calculated as 1.04 year^?1 for males and 1.11 year^?1 for females. The size (L₅₀) and age at first maturity (A₅₀) were estimated to be 29.1 cm TL and 2.8 years for males, 27.7 cm TL and 2.7 years for females and 28.0 cm TL and 2.8 years for both sexes combined. The results of this study provide the first information on the biology and population dynamics of C. lucerna in the Irish Sea, the first data collected in the northeast Atlantic since 1985 and the most northerly population studied to date.     

Feeding habits of longfin gurnard, Aspitrigla obscura (L.1764), along the Catalan coast (north-western Mediterranean)

The stomach contents of 372 specimens of Aspitrigla obscura (collected at quarterly intervals) have been analyzed to determine diet according to fish size and season. The results show that crustaceans (%No = 96%, %Weight = 76%) are the basic food. For all sizes, half of diet is assured by necto-benthic crustaceans. In smaller sizes, the remaining half is formed by planktonic species, whilst in larger sizes they are substituted by nycthemeral migrators. The importance of planktonic prey is greater in the winter sample than in the other samples. In every size, the feeding intensity is greater in the midday sample than in the morning one.     

Feeding of grey gurnard Eutrigla gurnardus (Triglidae) in the area of the Rockall Seamount

Specific features of feeding of grey gurnard Eutrigla gurnardus depending on vertical distribution and habitat conditions in the area of the Rockall Seamount in 2000 were considered. The intensity of feeding of grey gurnard from April to September decreased by several times. The main food of this species in spring are euphausiids and that in autumn are fish. Males feed slightly more intensively than females. The intensity of feeding, distribution, and behavior of grey gurnard in different seasons and at different depths near bottom and in the pelagial noticeably differ and depend on the composition of distribution and numbers of dominant food items (euphausiids, sand eel Ammodytes marinus, fish juveniles).     

Studies on feeding, growth and production of a recruited inshore population of Pleuronectes platessa (L.) at East Anglesey, North Wales

Trawl surveys in an area of 237 km² to the east of Anglesey (Irish Sea) indicated a population of recruited plaice ( c . 480000 fish) between 2 and 15 years old. Seasonal growth began in early April and annual growth in the dominant cohorts was analysed for males and females separately. Net annual production was estimated to be 0.17 g m^-2 from a standing crop of 0.3 g m^-2; c . 50% of the production is removed by fishing. The annual consumption (2.5 g m^-2) of Abra and Pectinaria was converted with 6.8% efficiency by weight (8.0% in energy units).     

Distribution and reproductive biology of the little cuttlefish Sepiola atlantica (Cephalopoda: Sepiolidae) around Anglesey, North Wales

Sepiola atlantica were captured in seine nets at twelve locations around the coast of Anglesey, UK. Animals were most abundant on the very sheltered shore of Y Foryd Bay and the wave-exposed shore of Traeth Penrhos, and these two locations were further sampled seasonally to examine the seasonal occurrence, population structure and reproductive biology of S. atlantica. Sepiola atlantica (5?C28?mm dorsal mantle length (DML)) migrated inshore seasonally and first appeared in July where they attained peak abundances between July and August at seawater temperatures of 17°C. Numbers declined between September and October as temperatures fell below 15?C16°C, and in late October, they migrated offshore. Male S. atlantica was significantly smaller and matured at a smaller DML than females. The number of spermatangia on the bursa copulatrix of female S. atlantica varied seasonally attaining maximum numbers in October with a mean of 22 spermatangia on the bursa copulatrix of Y Foryd Bay females. At Y Foryd Bay and Traeth Penrhos, the number of spermatophores in male and potential fecundity in female S. atlantica ranged between 1 and 147 and 25 and 141, respectively. The spermatophoric complex and gonadosomatic index showed a high degree of variability in individuals of similar wet body weight with the female gonad constituting a far greater percentage of the total wet body weight than the male gonad. It is concluded that S. atlantica of all sizes and maturity stages congregate in the shallow waters around Anglesey between July and October when environmental conditions are favourable for enhanced growth and maturation and where the high numbers of animals enhance opportunities for mating.     

On the life history of the lesser gurnard (Scorpaeniformes: Triglidae) inhabiting the Agulhas Bank, South Africa

Growth analysis based on sectioned sagittal otoliths revealed the lesser gurnard Chelidonichthys queketti on the Agulhas Bank to be relatively fast growing and long lived, with ages of up to 7 years being recorded. Total length at age (mm) was described best by the specialized von Bertalanffy growth model as L _T=306·1 (1 − e^{0·53(t+0·18)}). First approximations of total, natural and fishing mortality rates were determined at 0·73, 0·38 and 0·35 year⁻¹ respectively. The adult population was male dominated with a sex ratio of 1 female: 1·2 males with the mean size of males and females being similar. The lesser gurnard is an iteroparous species with females maturing by the end of the first year of life (195 mm L _T), thereafter spawning throughout the year with reproductive activity peaking over spring and late summer. The lesser gurnard appears to exhibit similar life-history patterns to other triglid species in that it can be classified as a generalist. Generalistic life-history characteristics such as a fast growth rate, early sexual maturity at a relatively large size, a non-seasonal spawning pattern, feeding on a variety of prey organisms and the ability to inhabit various substrata could all contribute to it maintaining a high biomass on the Agulhas Bank.     

Aspects of the reproductive biology of the sprat, Sprattus sprattus (L.) in inshore waters of the west coast of Scotland

Aspects of the reproductive biology of the sprat in inshore waters of the west coast of Scotland were investigated from August 1970 to July 1972. Spawning in sprat lasts for a period of five to six months, starting in February-March. Minimum size of maturity is 88–90 mm in both sexes but males tend to mature earlier in the season. Sprat shed their eggs in 7–10 batches. There is generally a higher proportion of females in the population. The fecundity ranges from 8700 to 46,600 in fish between 95 and 146 mm in length. It is significantly correlated to weight, length and age.     

Population biology of the little gulper shark Centrophorus uyato in Lebanese waters

A total of 38 individuals of the heavily exploited little gulper shark Centrophorus uyato were collected from Lebanese coastal waters using bottom longlines and trammel nets of different meshes at depths ranging from 115 to 600 m between May 2013 and February 2014. Their total lengths were between 45 and 94 cm and their total mass was from 870 to 6700 g. The sex ratio was not significantly different from 1:1, with 20 males and 18 females, but bathymetric sexual segregation occurred. Catch per net setting (CNS) was used as a relative abundance index to detect spatial distribution; trammel nets showed largest CNS ranging from 4·9 to 5·45 kg per unit effort in the north and south, at depths from 120 to 200 m, during spring and summer. The mass–length relationships demonstrated negative allometric growth (b < 3) (males: M_T = 0.3585L_T^2·071, r² = 0·94; females: M_T = 0.0239L_T^2·735, r² = 0·64). The condition factor as well as the gonado‐somatic and hepato‐somatic indices of C. uyato in the study area were also calculated. The results are discussed in relation to the distribution, growth and reproduction as well as the management of C. uyato.     

Population dynamics and conservation biology of the over-exploited Mediterranean red coral

The main goal of ecologists is nowadays to foster habitat and species conservation. Life-history tables and Leslie-Lewis transition matrices of population growth can be powerful tools suitable for the study of age-structured over harvested and/or endangered species dynamics. Red coral (Corallium rubrum L 1758) is a modular anthozoan endemic to the Mediterranean Sea. This slow growing, long lived species has been harvested since ancient times. In the last decades harvesting pressure increased and the overall Mediterranean yield reduced by 23. Moreover, mass mortality (putatively-linked to global warming) recently affected some coastal populations of this species. Red coral populations are discrete genetic units, gonochoric, composed by several overlapping generations and provided of a discrete (annual) reproduction. A population of this precious octocoral was studied in detail and its static life table was compiled. In order to simulate the trends overtime of the population under different environmental conditions and fishing pressures, a discrete, non-linear model, based on Leslie-Lewis transition matrix, was applied to the demographic data. In this model a bell-shaped curve, based on experimental data, representing the dependence of recruitment on adult colonies density was included. On these bases the stability of the population under different density, reproduction and mortality figures was analysed and simulations of the population trends overtime were set out. Some simulations were also carried out applying to the studied population the mortality values measured during the anomalous mass mortality event which really affected some red coral populations in 1999. The population under study showed high stability and a strong resilience capability, surviving to a 61% reduction of density, to a 27.7% reduction of reproduction rate and to an unselective harvesting affecting 95% of the reproductive colonies.     

Some aspects of the biology of gudgeon Gobio gobio (L.) in Irish waters

Data on some aspects of the biology of gudgeon were obtained during a programme of research on Irish coarse fishes. Eggs of gudgeon, were collected on 3 occasions—on June 8 and again on June 29, 1965 in a small rivulet entering a hydro-electric reservoir in Co. Cork; and on June 2, 1966 in a millstream on the Grand Canal in Co. Dublin. The eggs were greyish-white in colour, opaque, and 1·375–1·625 mm diam. Newly-hatched larvae from eggs from Co. Cork measured 5·45 mm and were distinguished by the presence of black pigment largely confined to the ventral aspect of the yolk sac and tail. They began to feed after 3 days; in 5–6 days the yolk was fully absorbed, the fish then measuring 6·2 mm. Following the creation of 2 hydro-electric reservoirs on the River Lee in Co. Cork, large populations of gudgeon developed in them for a time. It was found that, in the reservoirs, gudgeon less than 7·5 cm were feeding mainly on Cladocera, especially Chydoridae. The larger reservoir gudgeon and gudgeon in rivers and streams in Co. Cork fed mainly on molluscs, Gammarus, chironomid larvae, caddis larvae and ephemeropteran nymphs. Some gudgeon held a good deal of filamentous algae. Gudgeon were aged by means of scale reading, the results of which were confirmed by length-frequency distribution analysis in the case of the reservoirs. In the Lee system, gudgeon grew relatively rapidly at first, attaining a mean fork-length at 3 years old of 9·5–10·8 cm according to year-class. In the River Allow, a Cork Blackwater tributary, early growth was slower than in the Lee, but the length increments in the third and subsequent seasons were bigger than in the Lee reservoirs. In the Lee, most gudgeon of both sexes spawned for the first time when 2 years old, at a minimum fork-length of 6·9 cm in the case of males and 7·9 cm in the case of females. The trematode parasite Paracoenogonimus ovatus was of frequent occurrence in Irish gudgeon aged 2 years and upwards.     

The distribution, age and growth of wrasse (Labridae) in inshore waters of west Scotland

Wrasse were widely distributed in inshore waters of west Scotland in rocky and algal habitats. Ctenolabrus rupestris and Centrolabrus exoletus dominated commercial and experimental catches using creels, traps and fyke nets, but Crenilabrus melops, Labrus bergylta and L. mixtus were infrequent. Maximum age of sampled fish was 16yr in C. rupestris , 9 yr in C. exolefus , 5 yr in C. melops , 15 yr in L. bergylta , and 11 yr in L. mixtus . Growth was more rapid prior to maturation in all species. The von Bertalanffy growth model fitted data for C. rupestris and C. exoletus . Male C. rupestris and C. exoletus were significantly longer than females in most age groups and growth of all species captured in mid–Scottish areas was more rapid than in northern localities. Mortality (Z) of C. rupestris was 0–1861 per year and 0·4185 in C exoletus .     

An assessment of otoliths,dorsal spines and scales to age the long‐finned gurnard,Lepidotrigla argus,Ogilby, 1910 (Family: Triglidae)

Sagittal otoliths, dorsal spines and scales were critically assessed as structures to potentially determine the age of the long‐finned gurnard, Lepidotrigla argus. Counts were made of opaque growth increments and a readability score was assigned to each structure. Comparisons of growth increment counts were made between structures and between readings. All three structures showed some degree of readability and quantifiable growth increments, but this varied within fishes and between structures. Initial results showed that whole otoliths were more suitable to determine age estimates than dorsal spines and scales. Scales were considered unsuitable due to between reading ageing bias, variation in age estimates between structures, low precision and poor readability for this species. Dorsal spines showed evidence of loss of growth increments due to hollowing of the vascular core, which resulted in underestimation of older individuals in comparison to whole otoliths. Further analysis showed that growth increment counts from whole otoliths were lower for older individuals in comparison to sectioned otoliths. It is suggested that this is because of decreased clarity of growth increments towards the outer margin of whole otoliths in older individuals; this problem was not present with sectioned otoliths. It was concluded that sectioned otoliths were a more suitable structure from which to estimate age of L. argus than were whole otoliths, dorsal spines and/or scales.     

Investigations into the biology of the garfish, Belone belone (L.), in Swedish waters

Garfish, Belone belone (L.), were collected from commercial fishermen between May and September of 1987 from around the Swedish coast. Fish belonging to the year classes of 1983, 1984 and 1985 dominated the catch, with very few fish from the year classes of 1980, 1981 and 1982. Maturity stages and condition were investigated, and estimates of fecundity calculated; these ranged from 2193 to 10804 eggs per ripe female. Examination of gut contents showed fish, especially juvenile clupeids and gasterosteids, as well as isopods and amphipods, to be the most important components of their diet. Garfish populations from both the Baltic and the west coasts were parasitized by copepods of the genus Caligus . A study of meristic characteristics showed a significant difference between the number of vertebrae in fish from the Baltic and those captured on the west coast of Sweden.     

Reproductive biology of twoPrunus species (Rosaceae) in the Northwest Iberian Peninsula

We studied the reproductive biology ofPrunus spinosa andPrunus mahaleb (Prunoideae, Rosaceae) in the northwest Iberian Peninsula. The two species flowered at the same time (peaking on March 9 and 11, respectively in 1990) but differ significantly in their fruit maturation times. Nectar volume peaked in the early morning in both species, and was ten times greater inP. spinosa than inP. mahaleb. Neither species shows apomixis, nor does fruit-set occur if pollinators are excluded. In both species self-pollination resulted in fewer fruits than open pollination. The principal pollinators belong to theApidae family (79% and 63% of visits toP. spinosa andP. mahaleb, respectively). Results are compared with those for other rosaceous plants with fleshy fruits.     

闽西北梨瘿蚊发生经过与生活习性研究

梨瘿蚊Dasineura Pyri (Bouche)隶属双翅目,瘿蚊科,是福建省新发现的一种梨树害虫。该虫在闽西北建宁县黄花梨产区发生普遍,一些果园的春梢芽被害率达71.4-93.6％,造成树势衰弱,大幅减产,为搞清该虫发生习性,于1998－2000年对其进行观察研究,现将结果报道如下。