INVENTORY OF TIDEPOOL AND ESTUARINE FISHES IN ACADIA NATIONAL PARK Edited by Linda J. Kling and Adrian Jordaan School of Marines Sciences University of Maine Orono, Maine 04469 Report to the National Park Service Acadia National Park February 2008 EXECUTIVE SUMMARY Acadia National Park (ANP) is part of the Northeast Temperate Network (NETN) of the National Park Service’s Inventory and Monitoring Program. Inventory and monitoring activities supported by the NETN are becoming increasingly important for setting and meeting long-term management goals. Detailed inventories of fishes of estuaries and intertidal areas of ANP are very limited, necessitating the collection of information within these habitats. The objectives of this project were to inventory fish species found in (1) tidepools and (2) estuaries at locations adjacent to park lands on Mount Desert Island and the Schoodic Peninsula over different seasons. The inventories were not intended to be part of a long-term monitoring effort. Rather, the objective was to sample as many diverse habitats as possible in the intertidal and estuarine zones to maximize the resultant species list. Beyond these original objectives, we evaluated the data for spatial and temporal patterns and trends as well as relationships with other biological and physical characteristics of the tidepools and estuaries. For the tidepool survey, eighteen intertidal sections with multiple pools were inventoried. The majority of the tidepool sampling took place in 2001 but a few tidepools were revisited during the spring/summer period of 2002 and 2003. Each tidepool was visited once during late spring (Period 1: June 6 – June 26), twice during the summer (Period 2: July 3 – August 2 and Period 3: August 3 – September 18) and once during early fall (Period 4: September 29 – October 21). Physical characteristics of the tidepools were recorded along with the presence of other biological organisms like algae and invertebrates. Fish were collected, identified, counted, and measured for length. The number of tidepools containing fish did not vary much among sample periods. Twelve species of fish were identified in the tidepools. Initially, the dominant species were pollock, gunnels, and lumpfish. Pollock numbers decreased quickly and none were seen during either of the last two sampling periods. Gunnel numbers were relatively stable for the first two periods; however, their relative contribution to the catch declined during the second period due to an increased number of lumpfish caught during this period. Lumpfish were caught in 12 of the tidepools during the second sample period, suggesting a widespread occurrence. Nine tidepools contained lumpfish in the third sample period. A doubling in the number of gunnels in the third period and an increase in the number of mummichogs followed the influx of young of year (YOY) lumpfish. Gunnels were found in 13 tidepools during the third sample period. Large numbers of stickleback fry (three, four and nine-spine) and YOY mummichog were also documented to be abundant through the early summer in shallow estuarine mudflat pools and salt pannes. The mummichogs’ abundance is solely attributable to one site; the only tidepool to ever contain mummichogs. Atlantic sea snails increased in numbers over the course of the season and were most abundant in the last period. The short-horned sculpin also became relatively more numerous than the other species, largely due to the declining total number of fish captured. i We examined microhabitat variables (algal and grass abundance, invertebrate abundance and physical variables) associated with the presence, absence and abundance of tidepool fishes using principal component analysis (PCA), a multivariate statistical technique. Two important trends were apparent from the principal component analyses of tidepool fish data. First, fish presence and abundance became more predictable over the course of the season. Second, in all the sample periods there was a clear trend in the groupings of fish species. There were three primary types of tidepools, those where: (1) fish were absent, (2) mummichogs and fourspine sticklebacks were present, and (3) all other fish were present. Tidepools that were lacking in algal species, were also lacking in invertebrates and fish species. The separation of mummichogs and fourspine sticklebacks from all other fish species was largely controlled by the presence of the two different tidepool habitats around ANP: rocky ledges and mudflats. The two grouping of fish were clearly separated along these lines and there appears to be little overlap. The important physical parameters were always associated with vertical position relative to tide height, with the marine environment decreasing the temperature and increasing the salinity and the terrestrial environment increasing the temperature and decreasing salinity. For example, higher low tides resulted in reduced temperatures and increased salinities because of an greater marine influence. Whereas conditions in the high intertidal zone, being more influenced by the terrestrial environment, are likely to be more variable, with wet periods producing cooler and less saline conditions and dry periods producing warmer and more saline conditions. Salinity decreased during the year of this study. Early in the year, the physical characteristics of the tidepools were correlated with lower trophic level algal and invertebrate communities. Later in the season, the relationships between physical variables and algae/invertebrate species became non- significant, and the fish species correlated significantly with the algae and invertebrate species present. This suggests a cascade from physical factors contributing to algal and invertebrate species presence early to algal and invertebrate species correlating to fish species later in the year. Strong relationship between invertebrate and fish species presence suggest an important role of early season biological characteristics of tidepools, and their physical conditions such as relative height of the tidepool to the sea level, in structuring the eventual fish community. The progression of ecological structuring with season suggests that initial conditions are important in laying the foundation for later structure amongst fish species. Anthropogenic alterations to the trophic-shifting of ecological structure, through oil spills and physical disturbance, will therefore have effects beyond the time period in which they occur. Estuarine fish were inventoried during late spring and summer of 2002 and 2003, in five estuaries within Acadia National Park. Four estuaries were located on Mount Desert Island (MDI) and one was on Schoodic Point, the mainland section of ANP to the north of MDI. Physical characteristics of the estuaries were recorded along with the ii presence of other biological organisms like algae and invertebrates. Fish were collected, identified, counted, and measured for length. The results demonstrated that the location of culverts or sills relative to the mean tide height and local topography played an important role in structuring habitat characteristics. If the local relief is low and an impoundment of water is capable of collecting significant brackish water, the result is habitat suitable for dense populations of mummichogs and sticklebacks. Higher relief surrounding an estuary will only allow for a small pool of brackish water to form. The culverts also alter natural water column properties by forcing turbulent mixing and allow for substantial heating of the water over shallow mudflats and marshes. The differences in culvert placement within the estuaries of Acadia National Park have important effects on the flora and fauna. We documented that the pools of brackish water created by culverts allowed for populations of mummichogs and sticklebacks to outnumber any other species. It is not clear to what extent the impoundments negatively impact desirable species such as salmon, trout, and anadromous river herring. Management of marine species will require a comprehensive plan that includes freshwater processes. Past management, which focused on single species and systems, neglected species that move between habitats or ecosystems. A comprehensive plan will require the adoption of a broader view that incorporates different temporal and spatial scales. This may require that Park managers interact more with local, state and federal agencies charged with management of other systems. iii DEDICATION In tribute to Dr. John R. Moring, the contributors to this project would like to dedicate this work to his memory. John was a very productive writer, scientist, and teacher. He had a broad knowledge of both marine and freshwater fishes and was very interested in stream ecology, the effects of forest practices on fish habitat, and tidepool fishes. He was a dedicated teacher who, since 1979, was the major professor for 34 graduate students. He influenced many more undergraduate students throughout his tenure at the University of Maine. More importantly, he was an inspiring colleague, advisor, and friend. His friendly and gentle demeanor and quick wit are greatly missed by all those who had the honor of interacting with him, and serve as a great lesson in how to properly collaborate and advise within the academic world. Few are capable of appropriately melding personality and profession; John was one. Many people share the following sentiment regarding John: “he was one of the good guys”. iv TABLE OF CONTENTS Executive Summary ..........................................................................................................