Marine Environmental Research 57 (2003) 103–120 www.elsevier.com/locate/marenvrev Fish communities and life history attributes of English sole (Pleuronectes vetulus)in Vancouver Harbour Colin Levings*, Stacey Ong Fisheries and Oceans Canada, Science Branch, West Vancouver Laboratory, 4160 Marine Drive, West Vancouver, British Columbia, Canada V7V 1N6 Abstract Data on demersal fish abundance, distribution, and spatial variation in community composition are given for Vancouver harbour and a far field reference station in outer Howe Sound. Flatfish (F. Pleuronectidae) were the dominant taxa in the trawl sampling, with the English sole (Pleuronectes vetulus) one of the most abundant species, especially in Port Moody Arm. Cluster and ordination analyses suggested a different community in Port Moody Arm relative to the outer harbour and the reference site. Length data from English sole suggested the Vancouver harbour fish may be from a different population relative to the far field reference station, with more juveniles in the harbour. Both male and female English sole were older and larger in Port Moody Arm and females were more common in this area. Growth rates of female English sole were slower at Port Moody and Indian Arm in comparison to the central harbour. Feeding habits of English sole were different at various parts of the harbour, with possible implications for con- taminant uptake. The diet of English sole was dominated by polychaetes in Port Moody Arm and by bivalve molluscs at the far field reference station. Fish from the middle and outer harbour fed on a mixture of polychaetes, bivalve molluscs, and crustaceans enabling multiple pathways for bioaccumulation of pollutants. # 2003 Published by Elsevier Ltd. Keywords: Fish; Feeding; Habitat; Life history; Sediments; Pollution tolerance; Chemical pollution; Community function * Corresponding author. Fax: +1-604-666-3497. E-mail address: [email protected] (C. Levings). 0141-1136/$ - see front matter # 2003 Published by Elsevier Ltd. doi:10.1016/S0141-1136(03)00063-1 104 C. Levings, S. Ong / Marine Environmental Research 57 (2003) 103–120 1. Introduction The species composition of fish communities has been proposed as a key variable to assess the biological integrity of estuarine ecosystems (Deegan, Finn, Ayvazian, Ryder-Kieffer, & Buonaccorsi, 1997) and can also be used as a monitoring variable to detect changes in coastal water quality (Horn, 1979). In this paper, we describe the spatial changes and relative abundance of demersal fish in Vancouver harbour caught during the PICES Workshop and provide an analysis of fish community variation in this area. Demersal fish are bottom dwelling species which are in contact with the seafloor, and their biological characteristics are thought to reflect sediment conditions such as the presence of contaminants and changes in fish food inverte- brates. There are some baseline data available on demersal fish communities in Vancouver Harbour collected in 1985 (Goyette & Thomas, 1987), but in general the ecology of this taxocene is poorly documented in Vancouver Harbour. English sole (Pleuronectes vetulus) was identified as a dominant demersal species and was used as an indicator species in earlier work in the harbour by Goyette and Boyd (1989) and in several recent studies in Puget Sound (Collier, Johnson, Stehr, Meyers, & Stein, 1998). The physiological and health status of individual English sole was studied extensively by other investigators in the PICES Workshop (Bolton, Stehr, Boyd, Burrows, Tkalin, & Lishavskaya, 2003; Miller, Addison, & Bandiera, 2003; Stehr, Myers, Johnson, Spencer, & Stein, 2003). To complement their work, and to gain an insight into possible modes of contaminant effects on English sole basic information on length, weight, age, feeding, and growth was obtained from autopsied specimens. 2. Methods 2.1. Field sampling A small otter trawl (mesh size in body/wing 38 mm, 3.2 mm in codend; width of opening estimated 4.9 m) was towed by the NOAA vessel HAROLDW. STRE- ETER at five stations, on a presumed pollution gradient from the inner to outer Vancouver Harbour and into Howe Sound (Levings, Stein, Stehr, & Samis, 2003). Station T-38 was considered representative of Port Moody Arm; Station T-48 of the Indian Arm location; T-11B of the central harbour; T-49 of the outer harbour; and T-50 of the far field reference location in Thornbrough Channel. Each station was sampled between three and seven times. The net was towed between 5 and 10 min, and sampled an estimated area of between 1643 and 8570 m2 in each trawl (Table 1). Coordinates of the trawl locations and other basic sampling data are given by Stehr and Horiguchi (2001). The total catch from each trawl was sorted by species, then enumerated by species and weight. The larger invertebrates such as Dungeness crab (Cancer magister), tan- ner crab (Chionocetes tanneri), anemone (Metridium spp.) and a few species of bivalve molluscs were also enumerated and weighed. Fish catch data were standardized to C. Levings, S. Ong / Marine Environmental Research 57 (2003) 103–120 105 Table 1 Number of trawls, depth ranges, and estimated sample area for trawl samples in Vancouver harbour and Thornbrough Channel Site name Station name No. of trawls Depth range (m) Sample area (m2) Port Moody T-38 3 11–14 10896 Indian Arm T-48 3 26–30 15224 Central harbour T-11B 4 24–26 23642 Outer harbour T-49 6 30–45 38359 Thornbrough Channel T-50 3 55–73 12131 100 m2 using the sample areas shown in Table 1. When available, the total length (mm) of about 100 English sole from each station was obtained. We refer to these data as the general population length data. Data on weight, stomach content, and age were obtained for each English sole specimen autopsied by Stehr et al. (2003) for physiological condition and histopathology. The minimum size for the latter studies was 25 cm, the approximate length of sexual maturity for this species. After autopsy, the stomach was removed from each fish and preserved in 10.0% formalin. For aging, the right otolith was removed and placed in a glycerol-thymol mixture. The raw data from each trawl catch, fish ages, and stomach content data are presented elsewhere (Stehr & Horiguchi, 2001). 2.2. Laboratory methods Contents of a random sample of ten English sole stomachs from each station were examined in the laboratory. A Wild M-5 Stereomicroscope was used to enumerate organisms, which were identified to the major group level. Ages were determined by the Fish Aging Unit, DFO Science Branch, Pacific Biological Station, Nanaimo. Condition factor was computed using Fulton’s K where K=wt/l3Â105. 2.3. Statistical methods Parametric tests, primarily ANOVA analyses were used to determine the sig- nificance of biological parameters such as abundance, length, and age distributions, with chi-square used for proportion data. A cluster analysis using the weighted pair group average linkage method (Statistica, Statsoft, Tulsa, OK) was used to investi- gate community structure using standardized numerical catch data from each of the five stations, averaged over all the replicate trawls. The latter data were also used in a principal component analysis. The Shannon index of species diversity (H0) and evenness (E) for each station was calculated using the formulae: s 0 H ¼ -fg sum pilogpi i¼1 106 C. Levings, S. Ong / Marine Environmental Research 57 (2003) 103–120 Where i is the proportion of the total sample belonging to ith species (average numerical data) and E ¼ H0=ln S Where ln S is the natural logarithm of the total number of species found at a station. 3. Results 3.1. Fish community data Mean number of species obtained in each trawl ranged from 11Æ0.5 (Mean- ÆSEM) at Port Moody Arm to 12.2Æ0.2 at the outer harbour (Fig. 1a). However based on the total number of species caught in the trawls at a particular site, the fish community at the central harbour was most diverse (19 species), and Port Moody Arm least diverse (12 species). The other stations showed intermediate values in number of species: Indian Arm, 16 species; the outer harbour, 17 species; and Thornbrough Channel, 17 species. Mean biomass ranged from 0.65Æ0.1 kg.100 mÀ2 (meanÆSEM) at Port Moody Arm to 0.15Æ0.1 kg.100 mÀ2 at the Central Harbour, and number of individuals 10Æ5.100 mÀ2 (meanÆSEM) to 2Æ0.3.100 mÀ2 at the latter two stations (Fig. 1b and c). Twenty-nine different fish species were obtained in the trawls (Tables 2 and 3, Appendix A). Flatfish (Pleuronectidae and Bothidae) were the most common spe- cies, especially English sole (P. vetulus), Starry flounder (Platichthys stellatus), Flat- head sole (Hippoglossoides elassodon), Dover sole (Microstomus pacificus), Rex sole (Errex zachirus), Slender sole (Lyopsetta exilis) and Rock sole (Pleuronectes bilinea- tus). Flatfish were the dominant taxa at the Port Moody Arm station accounting for more than 50% of the fish caught there. Other dominant species were the Pacific tomcod (Microgadus proximus) at Port Moody Arm, Indian Arm and the Central Harbour. The Blackbelly eelpout (Lycodes pacificus) was the most abundant species at the outer harbour. The latter species was the only dominant species that was not caught at Port Moody Arm (Table 2). Percentage species composition at the five sites differed significantly (P<0.05) after testing with w2. Species diversity ranged from about 1.4029 at Port Moody to 1.8261 at the outer harbour, and evenness showed a narrower range, from approxi- mately 0.5843 to 0.7337 (Fig. 2). Neither statistic showed significant statistical var- iation over the five sampling stations (P>0.05). Results of the cluster analysis showed that the fish community at Port Moody Arm was the least similar (3%) relative to the cluster of the other locations.