Corkwing Wrasse Symphodus Melops Research Articles

Population Status, Breeding Biology and Diet of Norwegian Great Cormorants

Two subspecies of the Great Cormorant breed in Norway, the continental Phalacrocorax carbo sinensis in the south, along the Skagerrak coast, and the marine P. c. carbo from central Norway and northwards. Here we review the information existing until 2017 on population status and trends, breeding performance and diet of these two subspecies in Norway. The most recent national population estimates are approximately 2500 (in 2012) and 19,000 (in 2012–2014) breeding pairs of sinensis and carbo, respectively. The sinensis population established itself in 1996 in Rogaland at the south-western tip of Norway, and in 1997 in Østfold close to the Swedish border; in both areas it increased for about ten years. Since then, the numbers have stabilised. For carbo, the population increased from 21,000 pairs in the early 1980s to 27,000 in 1995, and then decreased to the current number of 19,000 pairs. Significant annual variations in clutch size and reproductive output have been observed, but the drivers of these changes have not been identified. Unidentified gadoids and Atlantic Cod Gadus morhua were the most common prey of carbo, whereas inshore species such as Corkwing Wrasse Symphodus melops, Rockcook Centrolabrus exoletus, Goldsinny Wrasse Ctenolabrus rupestris and Black Goby Gobius niger were the most common prey in the eastern Skagerrak caught by sinensis. Carbo took very large numbers of 1–3-year-old gadoids during the year, and we cannot exclude the possibility this can have local effects on fish mortality rates.

First Report of Symphodus melops (Linnaeus, 1758) with Maximum Length in the Black Sea

An individual of corkwing wrasse Symphodus melops (female) was captured by trammel nets on May 15, 2020, at 20 m depths from Ordu, the southern Black Sea coast. The total length and weight were measured as 320 mm and 520 g. The specimen was female with a gonad weight of 42 g and it was determined to be eight years old. This is the first record for the S. melops from the Black Sea. Its total length and weight were the maximum observed values for the species for the World. The paper is considered to contribute to fisheries biology and international scientific literature.

Mind the Depth: The Vertical Dimension of a Small‐Scale Coastal Fishery Shapes Selection on Species, Size, and Sex in Wrasses

AbstractSmall‐scale fisheries (SSFs) tend to target shallow waters, but the depth distributions of coastal fish can vary depending on species, size, and sex. This creates a scope for a form of fishing selectivity that has received limited attention but can have considerable implications for monitoring and management of these fisheries. We conducted a case study on the Norwegian wrasse fishery, a developing SSF in which multiple species are caught in shallow waters (mean depth = 4.5 m) to be used as cleaner fish in aquaculture. Several of these wrasses have life histories and behaviors that are sensitive to selective fishing mortality, such as sexual size dimorphism, paternal care, and sex change. An experimental fishery was undertaken over three sampling periods in 2018. Data on catch, length, and sex of wrasses across a depth gradient (0–18 m) were collected and analyzed. We found that depth distributions were species specific and the vertical overlap with the fishery was high for Corkwing Wrasse Symphodus melops and Ballan Wrasse Labrus bergylta, which were most abundant at depths less than 5 m. Three other wrasse species had invariant or increasing abundance with depth and were therefore less likely to be negatively impacted by this fishery. Body size was positively correlated with depth for these wrasses, and sex ratio became more male biased for the Corkwing Wrasse, the only species that could be visually sexed. This study demonstrates that depth can have strong effects on fishing selectivity at multiple scales and that such knowledge is necessary to develop management strategies that balance fishing mortality sustainably across species, sizes, and sexes. We recommend that management priorities be directed toward the Ballan and Corkwing wrasses—the species having the highest vertical overlap with the fishery. Furthermore, CPUE was strongly affected by seasonality and positively correlated with increasing wave exposure for one of the species. This underscores the general importance of standardizing catch data for several environmental covariates when monitoring species that are affected by SSFs.

Sea lice prevention strategies affect cleaner fish delousing efficacy in commercial Atlantic salmon sea cages

Over the last 2 decades, cleaner fishes have been employed to remove external sea lice parasites from Atlantic salmon Salmo salar in sea cages. Norway, Scotland, Ireland, and the Faroe Islands combined now use ~60 million cleaner fish per year. While small-scale experiments demonstrate the efficacy of cleaner fishes, industrial-scale sea cages have multiple structures and conditions that create different environments, which may impact cleaner fish efficacy and welfare. Here, in commercial sea cages, we investigated if 4 different anti-lice strategies impacted the delousing efficacy, physical condition, and behaviour of cleaner fish (corkwing wrasse Symphodus melops). The strategies tested were: (1) cleaner fishes only; (2) cleaner fishes and functional feed; (3) cleaner fishes, functional feed, and deep lights and feeding; and (4) cleaner fishes, functional feed, deep lights and feeding, and lice skirts. Corkwing wrasse were sampled from 3 cage-level replicates of each anti-lice strategy 3 times over 2 mo. Lice levels on salmon were recorded every 3 to 4 wk. Only 11% of corkwing wrasse had salmon lice in their gut, with individual wrasse having up to 72 lice in their stomach. Wrasse in cages encircled by lice skirts consumed one-ninth as many lice as those in other anti-lice treatments and had less overall impact on the number of lice per salmon. Fin, skin, mouth and eye condition, K factor, and observed cleaning behaviours of corkwing wrasse were similar across all anti-lice strategies. Our results demonstrate that different in-cage anti-lice strategies altered the magnitude of lice consumption in corkwing wrasse at this site and for this production period. Moreover, while a small proportion of corkwing wrasse appear to target lice as prey, most individual corkwing wrasse were ineffective biological control agents in a full-scale farm setting.

High nervous necrosis virus (NNV) diversity in wild wrasse (Labridae) in Norway and Sweden.

Wild goldsinny wrasse Ctenolabrus rupestris, corkwing wrasse Symphodus melops and ballan wrasse Labrus bergylta were collected at 8 sampling sites in Sweden and Norway during summer 2014. Brain tissue from 466 wrasses were analyzed for nervous necrosis virus (NNV) infections by real-time RT-PCR, and positive samples were subjected to sequencing and phylogenetic analysis of partial segments of the RNA2 and RNA1 genes. This study shows that NNV is present in wild ballan, corkwing and goldsinny wrasse along the coastline of Sweden and Norway. The overall prevalence in the sampled labrids was 6.7%. Prevalence was 6.4% in goldsinny, 6.3% in corkwing and 18% in ballan wrasse. The wrasse RNA2 NNV sequences revealed high genetic variability and were divided into 3 clusters within the cold water barfin flounder NNV (BFNNV) and warm water cluster red-spotted grouper NNV (RGNNV) genogroups. Within the BFNNV genogroup, wrasse NNVs clustered in 2 sub-genogroups, with grey mullet NNV (GMNNV) and with Atlantic halibut NNV (AHNNV). These groups were previously dominated by virus originating from Atlantic cod Gadus morhua and Atlantic halibut Hippoglossus hippoglossus from the northeast Atlantic. The presence of NNV in wild wrasse and the surprising high genetic variability observed in this study should be considered before moving wild-caught wrasse between geographically distant sites. The results show that use of wild-caught wrasse as brood fish in wrasse farming represents a risk of introducing NNV into aquaculture.

Vibrio tapetis-like strain isolated from introduced Manila clams Ruditapes philippinarum showing symptoms of brown ring disease in Norway

The Manila clam Ruditapes philippinarum was introduced to Norway in 1987 and was produced in 2 hatcheries until 1991. Clam seed was planted at 6 sites. Two sites were on the Island of Tysnes, south of Bergen. Surviving adult Manila clams were recovered in 1995 and 1996. In the present study, Manila clams from the original seeding that displayed morphological signs of brown ring disease (BRD) were recovered in June 2003 (n=7) and in June 2004 (n=17). Samples from extrapallial fluid, tissues and haemolymph were inoculated on marine agar. Replicate subcultures on selective media were used to select potential Vibrio tapetis strains, and in total, 190 bacterial strains were isolated. One of these strains clustered within the V tapetis clade and was named NRP 45. DNA:DNA hybridisation with the type strain CECT4600 showed 52.7 and 57.3% DNA:DNA similarity. Hybridisation of NRP 45 and the V tapetis LP2 strain, isolated from corkwing wrasse Symphodus melops, produced 46.6 and 44.4% re-association. Partial gene segments encoding 16S rRNA, gyrase B protein (GyrB) and chaperonin 60 protein (Cpn60) were characterised and compared to CECT 4600. NRP 45 showed 5 differences in the 1416 nucleotides (nt) of the 16S rRNA encoding gene (99.6% similarity), while the GyrB encoding gene had 62 substitutions of 1181 nt compared (94.8% similarity) and the Cpn60 encoding gene had 22 substitutions out of 548 nt compared (96% similarity). This is the first finding of BRD and the first isolation of a V. tapetis-like bacterial strain from a bivalve in Norway.

Susceptibility of corkwing wrasse Symphodus melops, goldsinny wrasse Ctenolabrus rupestis, and Atlantic salmon Salmo salar smolt, to experimental challenge with Vibrio tapetis and Vibrio splendidus isolated from corkwing wrasse

The virulence of two Vibrio strains, previously isolated from diseased corkwing wrasse Symphodus melops and identified as V. tapetis and V. splendidus, to corkwing and goldsinny wrasse Ctenolabrus rupestris and to Atlantic salmon Salmo salar, was studied under laboratory conditions. Both bacteria were shown to be opportunistically pathogenic to corkwing wrasse, causing significantly higher mortality in the challenged groups than in the controls. Bacterial cultivation of kidney samples and re-isolation of V. tapetis and V. splendidus from most mortalities confirmed the two strains as the probable cause of mortality in the challenged groups. The control group also suffered relatively high mortality, but no specific pathogens that were suspected to be the main cause of death were isolated, other than a mixture of Vibrio spp. and, in the case of one individual, atypical Aeromonas salmonicida. Following injection challenge with both bacterial strains, no mortality was recorded in Atlantic salmon. In bath challenge trials with goldsinny wrasse, only slight mortality was observed in the challenged groups and the unchallenged control group. Bacterial examination showed that atypical Aeromonas salmonicida was the probable cause of death in both bath challenged and control groups of goldsinny wrasse, and no indication of infection by any Vibrio sp. was found.

Characterization of strains of Vibrio splendidus and V. tapetis isolated from corkwing wrasse Symphodus melops suffering vibriosis.

Two vibrio bacteria pathogenic to the corkwing wrasse Symphodus melops were isolated. Vibriosis-inducing strain LP1 was isolated as the dominanting bacterium in kidney samples of dead and moribund wrasse from a population suffering vibriosis and high daily mortality in 1998 on the Norwegian west coast. The other vibriosis-inducing strain, LP2, was isolated from wrasse captured the following year. Re-infection experiments have confirmed that these strains cause vibriosis in corkwing wrasse. Both strains were typical vibrios sharing the traits of fermentative Gram-negative curved rods with motility and a positive oxidase reaction. Detailed biochemical and genetic characterisation revealed a close affiliation to known species of the marine environment. The first isolate, LP1, is a form of the ubiquitous seawater organism Vibrio splendidus, while the second isolate, LP2, is closely related to V. tapetis (previously only known as the brown ring disease agent in clams). Identification of the new wrasse pathogens V. splendidus LP1 and V. tapetis LP2 is facilitated by break points observed in this study.

Variation in Plasma Steroids and Reproductive Traits in Dimorphic Males of Corkwing Wrasse (Symphodus melops L.)

Differences in plasma steroid levels may reflect behavioral, gonadal, or morphological specializations that characterize different male reproductive phenotypes in teleost fishes. In the present study, we investigated whether differences in plasma steroid levels exist between two distinct male morphs shown in the corkwing wrasse Symphodus melops. In addition, we examined differences in male reproductive traits, including gonad mass, sperm motility, and sperm concentration, between the two male types. Possible associations between plasma steroid levels and reproductive traits were also investigated. The results indicated that males with typical male secondary sexual characters (territorial males) had higher plasma levels of 11-ketotestosterone (11kT) compared to smaller males with female secondary sexual characters (female mimics). The female mimics in turn had higher plasma levels of both testosterone (T) and 17β-estradiol. In addition, female mimics had relatively larger gonads and longer-lived sperm than territorial males. Relative gonad mass covaried significantly with the plasma levels of 11kT and T among the morphs, indicating that the relative gonad size correlates positively with the plasma level of these two steroids. However, there was no significant covariance between sperm traits and plasma steroids for the two male morphs. Hence, our results do not indicate any causal link between sperm quality and hormones.

The Efficacy of a Single Intraperitoneal Injection of Flumequine in the Treatment of Systemic Vibriosis in Corkwing Wrasse Symphodus melops

In this investigation, the efficacy of a single intraperitoneal injection of flumequine in the treatment of systemic vibriosis in corkwing wrasse Symphodus melops was examined. In a population of corkwing wrasse that was experiencing daily mortality, the dominant bacterium cultivated from kidney samples of dead fish was tentatively classified as a species of Vibrio resembling V. splendidus. The infected fish were randomly divided into two groups, each of 60 individuals. Group 1 was treated with flumequine (25 mg/kg of fish) administered by a single intraperitoneal injection, whereas the fish from group 2 were injected with saline. The mortality was observed daily for 21 d. The cumulative mortality was significantly (P < 0.005) higher in the control group (58%) compared with the medicated group (11%). Bacterial examination of kidneys from dead and surviving fish of both groups indicated the Vibrio to be quickly and effectively eliminated by the antibacterial agent.

Phenotypic variation between dimorphic males in corkwing wrasse

The age‐frequency distributions for sneaker males (individuals with female secondary sexual characters) and territorial males (individuals with typical male sexual characters) of corkwing wrasse Symphodus melops in a Swedish population did not differ. Otolith analysis revealed that sneaker males were smaller than their territorial male counterparts as juveniles, but there was no evidence of a clear‐cut threshold to determine the subsequent reproductive patterns. Thus, the expression of male morph in corkwing wrasse most likely is related to early growth pattern and the different morphs could be fixed for life. Adult sneaker males in general were smaller than territorial males of the same age. The relative gonad size and the abdomen in sneaker males were substantially enlarged compared with territorial males, but there was no difference in gonad water content between the two types of males. Sneaker males weighed less in relation to their length than territorial males. These results support theoretical sperm competition models which predict that the male morph with reduced attractiveness to females (i.e. sneakers) should invest more into spermatogenesis in order to achieve fertilization than the attractive male morph (i.e. territorial males).

Phenotypic variation between dimorphic males in corkwing wrasse

The age-frequency distributions for sneaker males (individuals with female secondary sexual characters) and territorial males (individuals with typical male sexual characters) of corkwing wrasse Symphodus melops in a Swedish population did not differ. Otolith analysis revealed that sneaker males were smaller than their territorial male counterparts as juveniles, but there was no evidence of a clear-cut threshold to determine the subsequent reproductive patterns. Thus, the expression of male morph in corkwing wrasse most likely is related to early growth pattern and the different morphs could be fixed for life. Adult sneaker males in general were smaller than territorial males of the same age. The relative gonad size and the abdomen in sneaker males were substantially enlarged compared with territorial males, but there was no difference in gonad water content between the two types of males. Sneaker males weighed less in relation to their length than territorial males. These results support theoretical sperm competition models which predict that the male morph with reduced attractiveness to females (i.e. sneakers) should invest more into spermatogenesis in order to achieve fertilization than the attractive male morph (i.e. territorial males).