Marine Habitats Prior to Onset of Ocean Warming in 1976, with Lists of Fish Predators F1 James R

F Marine Habitats Prior to Onset of Ocean Warming in 1976, with lists of Fish Predators F1 James R. Chess and Edmund S. Hobson U.S. DEPARTMENT OF COMMERCE NOAA-TM-NMFS -SWFSC-243 LR National Oceanic and Atmospheric Administration Tiburon Laboratory National Marine Fisheries Service Southwest Fisheries Science Center NOAA Technical Memorandum NMFS The National Oceanic and Atmospheric Administration (NOAA), organized in 1970, has evolved into an agency which establishes national policies and manages and conserves our oceanic, coastal, and atmospheric resources. An organizational element within NOAA, the Office of Fisheries is responsible for fisheries policy and the direction of the National Marine Fisheries Service (NMFS). In addition to its formal publications, the NMFS uses the NOAA Technical Memorandum series to issue informal scientific and technical publications when complete formal review and editorial processing are not appropriate or feasible. Documents within this series, however, reflect sound professional work and may be referenced in the formal scientific and technical literature. Cover photo- An aggregation of the caridean shrimp Lysmata californica under a ledge. NOAA Technical Memorandum NMFS JULY 1997 Benthic Invertebrates of Four Southern California Marine Habitats Prior to Onset of Ocean Warming in 1976, with lists of Fish Predators James R. Chess and Edmund S. Hobson National Marine Fisheries Service Southwest Fisheries Science Center Tiburon Laboratory 3150 Paradise Drive Tiburon, California 94920 U.S. DEPARTMENT OF COMMERCE N OAA-TM-NM FS -SWFSC-243 National Oceanic and Atmospheric Administration Tiburon Laboratory National Marine Fisheries Service Southwest Fisheries Science Center Benthic Invertebrates of Four Southern California Marine Habitats iii . CONTENTS Introduction ...................................................... 1 Methods ......................................................... 2 Study Sites ....................................................... 6 Benthic Invertebrates .............................................. 14 Sponges ................................................ 14 Hydroids ................................................ 15 Anthozoans.............................................. 15 Polychaetes .............................................. 16 Gastropod Molluscs ....................................... 22 r” Bivalve Molluscs ......................................... 32 Cephalopod Molluscs ...................................... 37 Ostracods ............................................... 39 Copepods ............................................... 44 Mysids ................................................. 46 Cumaceans .............................................. 47 Tanaids ................................................. 49 Isopods ................................................. 51 Gammaridean Amphipods .................................. 58 Caprellidean Amphipods ................................... 72 Brachyuran Decapods ..................................... 80 Caridean Decapods ....................................... 81 Bryozoans............................................... 83 Asteroids ............................................... 89 Ophiuroids .............................................. 89 Echinoids ............................................... 91 Holothurians ............................................. 92 Ascideans ............................................... 92 Acknowledgements ............................................... 95 ReferencesCited ................................................. 97 R Indexto Species ................................................. 107 Benthic Invertebrates of Four Southern California Marine Habitats ! INTRODUCTION This is an account of the benthic invertebrates in four distinct marine habitats at Santa Catalina Island, off southern California (Fig. 1). Although based on samples taken to iden- tify foods of fishes, it is, to our knowledge, the most comprehensive published account of species composition on rocky reefs. Also, in representing varied settings at this centrally lo- cated island, the findings permit comparisons with results of similar studies elsewhere in southern California. Potential for still more insight comes from lists of predators on each species, as trophic relations are key elements of ecological systems (Hobson 1994). The presentation is meant as a source of information that can be used several ways. Be- cause the assessments were made from 1973 to 1975, they describe conditions that were in place immediately before the extended period of elevated sea temperatures that began in about 1976 (McLain 1983, Cole and McLain 1989). Some investigators, therefore, may find the information usehl as a basis for measuring effects of the post 1976 warming on organisms and their environment. This warming has had profound effects among pelagic organisms (e. g., Roemmich and McGowan 1995, MacCall 1996), and might be expected to have had similar effects among benthic organisms. The information provided here may pro- vide baselines needed to examine this expectation. The informatioil presented may also be useful in the great extent that it defines the species involved. There is widespread contention that loss of species diversity is among the more damaging effects of human activities on ecological systems (e. g., Ehrlich and Wilson 199 1, Lubchenko et al. 199 1, Hughes and Noss 1992), and obvio- sly one needs measures of the diversity to document such loss. But measures of ben- 34" 33" 0 50 100 c-:3LIc--ic-:l San KILOMETERS Dieg 121" 120" 119" 118" 117" Figure 1. Area of the sea off southern California, with Santa Catalina Island. 2, Benthic Invertebrates of Four Southern California Marine Habitats thic diversity are invariably compromised by problems in the collection and identification of organisms. The nature and extent of these problems become clear on the pages that follow, which show what can be expected in measures of species diversity in the nearshore benthos. METHODS Samdina The benthos was assessed using SCUBA at sites off the western end of the Island (Fig. 2). Occurrences of invertebrates and algae were characterized with a standard set of Sam- ples and observations in 4 x 25-m transects at each of four primary sites: Isthmus Reef, Fisherman's Cove, West End and Eagle Rock. The first two represented leeward habits, the last two windward habitats. Three other leeward sites-Ship Rock, Lion's Head and Bird Rock-provided much supplemental information. The comprehensive assessments at the four primary sites were made between 0900 and 1500 hours, thus reducing the complexities of diel variability, Despite this emphasis on mid-day conditions, our conclusions incorpo- rate a broad knowledge of diel variations based on our other studies at this location (Hobson and Chess 1976, 1986; Hobson et al. 1981). The standard set of samples at each of the primary sites were taken during the montwyear as follows: Isthmus Reef-5/73, 9/73, 1/74, 3/74, 7/74, 10174, 2/75 and 7/75; Fisherman's Cove-5/73, 11/73, 3/74, 5/74, 8/74, 1/75, 4/75 and 7/75; West End-2/73,5/73,10/73,2/74,6/74,8/74 and 7/75; Eagle Roek-5/73, 9/73, 1/74, 5174,7174 and 7/75. 118'35'W - 118"30'W 33-30" 1 West End Ship Rock 33"25N 118'35'W Figure 2. Sites of assessments off western Santa Catalina Island. Benthic Invertebrates of Four Southern California Marine Habitats 3. The samples were of several types: Larger, exposed organisms were censused with visual counts, while others too small or cryptic to be enumerated this way were sampled with various collecting devices. Organisms on rock were sampled with an airlift (Fig. 3), while organisms on algae were sampled by collecting turf, and organisms in sediments were Sam- pled with coring devices. Each of these procedures will now be described in more detail. Visual Assessments Organisms quantified visually included the algae and certain large, conspicuous invertebrates, e. g., various sponges, anthozoans, molluscs and echinoderms. The algae were assessed several ways. Components of the benthic turf were assessed by an observer that hovered in the water column and estimated the percentage each major species contributed to the total algal cover on the sea bed below. Larger algae growing above the turf were quantified by counting individual plants and stipes. Also included were subjective evaluations of such features as canopy thickness, general condition and coverage by encrusting organisms. Invertebrates assessed visually were those seen in the transects. Most of these were rela- pbl* tively large, sedentary (if not sessile) forms ineffectively sampled by the other methods. I Only those of uncertain identity were collected. Collections of the Benthos Organisms on rocksurfaces were sampled with an airlift (Fig. 3), which uses a tank of compressed air to generate suction that pulls material from substrata into an intake nozzle (5 cm in diameter) and then through a 2.5 m-long tube to a nitex-mesh (0.333-mm) bag (20 x 50 cm). Each collection sampled a 0.25-in2quadrat. The more loosely attached organisms were dislodged by scraping the intake nozzle on the substrate, but this technique generally was ineffective with strongly attached forms. See Chess (1978) for more information on this device. Ovgunisms on benthic turfwere sampled with collections of the major turf algae. These were collected in bags (20 x 40 cm) of nitex mesh (0.333 m)that were placed over each plant and then closed while pulling the

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