All but one of the 2 dozen or so west-coast species of limpets live intertidally on that the relationship between desiccation resistance and distribution of sympatric . Many species of limpets overlap in distribution with barnacles and may. In contrast, the role of bottom-up effects (nutrients and productivity), Barnacles, in particular, have a long history of ecological study and have. On the central Pacific coast of Costa Rica, populations of Tetraclita .. destroy a direct relationship between larval settlement and subsequent recruitment where.
The first, near Paradise Cove, was composed of 20 automobile bodies; the second, near Redondo Beach, used 6 streetcars. The success of these reefs, routinely observed each month for over 2 years, was based primarily on the observation of fish increases. Invertebrate and algae growths were only superficially noted. Analysis of data obtained from these first experimental reefs Carlisle, Turner, and Ebert, revealed wide variations in the number of fishes present on a given day.
Some of these variations were explained as expected seasonal fluctuations; others concided with variations in water clarity. The remainder appeared to reflect a preference by the fishes for a given material.
To evaluate this apparent preference a replication reef experiment was proposed and designed. The present report discusses in detail our findings from over 4 years of studying these reefs. In addition, observations were made on a non-experimental "production model" reef, and various natural areas. Money to build the replication reefs was received from the California Wildlife Conservation Board. Each reef was composed of tons of class B quarry rock, one streetcar, 14 automobile bodies, and 44 concrete shelters; the total cubic area of each material was calculated to be nearly equal to that of any of the other materials.
Each of the four materials formed a corner of each reef, and was placed from to feet from its nearest neighbor, to allow separate fish populations to build up around each materia. Our earlier studies Carlisle, et al. Later observations indicated this held true where foot distances prevailed, but not in areas separated by only feet.
Our first production-model reef was constructed of 1, tons of class B quarry rock stone of approximately 1, pounds each deposited in four, foot diameter piles in 75 to 80 feet of water. It was located near the Redondo submarine canyon, some 2, yards SW of the Redondo Beach fishing pier. The general area was first traversed by the diving boat and fathograms were made of the bottom.
Extensive flat sand or muddy-sand areas were then visually surveyed by biologist-divers. While swimming along a yard m transect line, these two- or three-man diving teams recorded the various physical and biological characteristics of the area; water clarity and temperature, bottom type, ripple marks, currents, and animals and plants.
After we used a diver-held fathometer to search for rocky outcroppings or artifacts beyond our sight but still within feet of the transect line [ Figure 2 ]. Turner horizontally surveying the sea floor with a diver-held fathometer. Photo by Earl E. Fathometer contacts were visually verified, and the potential effect of each on the proposed reef was postulated. If extensive outcroppings or large artifacts, considered as competition for the new reef, were found we recommended alternate sites.
Small artifacts or single rocks were ignored. A foot depth was chosen for the multi-component reefs because this allowed the divers considerable survey time without involving prolonged decompression. Shallower depths were avoided because the increased surge could hamper our surveys and the reefs would be hazardous to navigation. Nearshore reefs, again examined only incidentally, have been built around the periphery of fishing piers, at depths of only 12 to 24 feet. After selection of a suitable site, permits have been obtained from the U.
Navy was also notified of our intent and the U. Fishing interests, both commercial and sport, have been contacted as were any other interested agencies.
Photo by Charles H. The Bay floor slopes gently seaward forming a shelf 3 to 6 miles wide. In this study, our interest was primarily with the topography of this center shelf—the site location of the three replication WCB and the "production model" Redondo Canyon reefs.
The shelf is generally characterized as being "smooth" and gently sloping seaward to approximately 50 fathoms Figure 1. Although the term "smooth" is used, in some places local relief is extensive enough to limit the effectiveness of a man-made fishing reef. The "bottom dump," compartmented barge, bringing the rock from a quarry on Santa Catalina Island, about 25 miles away, had only to come near this temporary buoy, open its doors, and let the rock fall [ Figure 5 ].
The location for each of these, with reference to the rock, was random, but the general configuration of each reef was designed to form a square Figure 1. The 14 automobile bodies were lashed together in groups of two, three or four [ Figure 6 ] to prevent movement in a strong surge, and the 44 concrete shelters were made into pyramids of three, with two on the bottom and one across the top [ Figure 7 ] to counteract "sanding-in.
This buoy had drifted several hundred feet when the divers arrived and learned of the mishap. A second buoy was immediately placed and the area searched for the rock; unfortunately, our efforts at that time were futile. This second temporary buoy was then permanently anchored and the rest of the reef constructed around it. After this until the study terminated in June the surveys became sporadic; our concern being only with new occurrences and a general notation of conditions.
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The majority of observations were made on the Hermosa Beach reef because of its proximity to our boat launching facilities. The Redondo Canyon production model reef was constructed in January and although it too was easily accessible from our launching area, we visited it infrequently, concentrating our efforts upon the three experimental reefs. Observations and sampling conducted at each reef included: Details of these sampling methods are appropriately discussed in the sections dealing with each topic.
Pre-reef data were obtained from catch records, prior surveys by other organizations, and by visual observations we made during the reef-site selection surveys Table 1. Underwater observations were recorded, during each dive, on opaque white plastic sheets [ Figure 8 ], using a flexible plastic pencil.
This flexible pencil proved more durable than standard wooden ones. Strachan recording fish behavior notes on a plastic slate; note the compass and collecting bag. Photographs of the reefs, the various invertebrates, and the fishes were taken underwater with Rollei-marine and Calypso underwater cameras, and on the surface with these, an Exa and a Speed-graphic. Motion pictures of reefs and survey operations were taken with both Fenjohn and Sampson-Hall 16 mm underwater cameras.
These survey dives varied in duration from a few minutes to several hours. Although assistance was received from other divers on several occasions, one or more of the authors was present on each dive. Salinity, often an important limiting factor in the sea, was not measured during this study.
In the open ocean, salinity varies within narrow limits as opposed to estuarine waters where wide seasonal fluctuations may occur. For example, Stevenson, Tibby and Gorsline reported a rather constant Floral and faunal distributions, seasonal fluctuations, attachment of sessile organisms, and reproductive cycles are all contingent upon and either directly or indirectly related to temperature regimes. During this study, temperature data were obtained with a diver-held standard bucket thermometer.
Readings were taken at the bottom at the termination of each dive, then at successive foot increments to and including the surface. The time of day and the months in which temperatures were recorded at each reef varied considerably.
Likewise, the number of observations in any one month were not constant, ranging from zero to six. The paucity of data from the Santa Monica and Malibu reefs, particularly inresulted from the emphasis placed on studying the Hermosa Beach reef; it was established as the standard and the others compared to it.
Weather, launching facilities and travel time were all factors contributing to this decision. Surface temperatures at the Hermosa Beach reef ranged from The lowest bottom temperature Seasonally, low surface temperatures were found from November or December through May. Low bottom temperatures prevailed from March through July. Temperature patterns and seasonal ranges at the Santa Monica and Malibu reefs were comparable to those recorded at the Hermosa Beach reef.
At each, isothermal conditions occurred in the winter and maximum stratification in the summer [ Figure 9 ]. The upper line reflects the surface waters, the lower line the bottom temperatures foot depth Sublittoral temperature patterns along the southern California coast appear to be quite similar, at least to depths of feet. Typically a vertical thermal stratification initiates by late February or early March precipitated by increasing air temperatures and subsequent warming of the surface layer.
This thermal gradient continues its development through spring and into early summer as prevailing westerly winds move surface water away from the coast and upwelling occurs. At this time, the bottom water begins to warm as upwelling diminishes.
Maximum thermal stratification generally occurs in August and as fall approaches the gradient collapses. Cooling air temperatures combined with wind mixing of the upper surface layers result in nearly isothermal conditions by November or December.
During the frequent summer blooms of dinoflagellates, where a "red water" condition occurs, this thermocline acts as a barrier, restricting these dinoflagellates to the warmer surface water.
Divers working beneath the thermocline during these periods often find that good visibilities, but eerie colors, prevail due to the red-filter effect from the surface concentrations of plankton. Turbidity, resulting from suspended sediments, may be limiting for algae and many of the sessile filter feeding animals. Conversely, sedimentary tube building worms and a host of other attached animals often require these sediments to impregnate their outer layers for strength, protection and additional growth.
Characteristic biotic communities thus serve as excellent indicators of the turbidity normal to an area. Additionally, reduced water visibilities limit the effectiveness of diving surveys e. We estimated water visibility on each dive to describe the general conditions under which our more-detailed biological observations were made.
These estimates were the maximum horizontal distances at which most swimming fishes were recognizable. To standardize these estimates and to obtain an index which would be meaningful to other scientists, we also made horizontal Secchi disc readings.
One diver held the Secchi disc while another swam out with a measured line—a right angle interpretation of the standard shipboard method. When our estimated water visibilities were plotted against the Secchi disc measurements, they revealed an approximate 2: Water visibilities fluctuated widely without apparent correlation to season or tide; although best visibilities are purported to occur during the fall, in the absence of storms.
As with temperature readings, we made fewer monthly visibility estimates at the Santa Monica and Malibu reefs in The maximum sea floor visibility, estimated as 35 feet, occurred at the Hermosa Beach reef Junehowever, on several occasions bottom visibilities here were estimated at only 1 foot. Moderately good visibilities about 10 feet were experienced frequently at this reef but seldom at Santa Monica and Malibu [ Figure 11 ].
Poorest visibilities were generally encountered at Santa Monica, where only once the estimated sea floor visibility exceeded 10 feet—in August13 feet was estimated. Here, sea floor visibilities averaged 4 to 5 feet.
Water visibilities encountered in Santa Monica Bay could generally be described as marginal for conducting diving surveys. Four-foot visibility appears minimal for properly assessing reef fish populations; with less visibility an overall perspective cannot be obtained.
Fine hard-pack sand is a prime base.
Shifting of such sediments is minimal and objects placed on them will not "sand-in", assuming that the water depth is sufficient to negate onshore wave turbulence. Coarser sand with deep ripple marks indicating strong water action and shifting bottom sediments is less desirable due to the likelihood of materials to "sanding-in", especially those of low relief.
Any sizeable structure placed on a normally flat ocean bottom can be expected to produce certain local changes on the surrounding substrate. Such changes, even if subtle and not readily evident in general field observations, are important in assessing the value and effect of the artificially introduced reef-type structures. Comparative analyses of bottom sediments taken from "construction" sites before and after reef placement will show the character and magnitude of any prolonged substrate alteration.
Unfortunately, we made only a general analysis of the bottom sediments prior to reef placement in Santa Monica Bay. However, records of bottom sediments from areas adjoining the reef sites Hartman, ; Terry, Keesling, and Uchupi, are available for comparison.
In general, the Hermosa Beach reef site is an area of gray sand with an intruding tongue of "red" sand in its NW corner. At Santa Monica the bottom is green silty sand, and at Malibu it is medium green sand with much flocculent dark debris, presumably derived from nearby streams which seasonally empty into the ocean. We made detailed analyses of sediments at two of the three multiple component reef sites near the end of our study, 3 years after reef placement.
These supplemented general sediment observations made during our routine surveys. Core penetration varied with bottom conditions. The samples were not taken randomly but plotted to give the most significant picture of the reef's effects on the substrate at varying distances from the actual structures. The core samples thus obtained were divided into two main categories: The dried core was then cut into three subequal parts called "top," "middle," "bottom"weighed and washed through a series of standard Tyler screens.
Resulting fractions were again dried and weighed. The weight differential between pre- and post-washing was recorded as the silt-clay fraction—the amount passing through the 62 micron mesh screen.
The various fractions were designated as coarse, fine, etc. Because sediment samples had not been taken previous to reef placement we took cores adjacent to, and a measured distance from, the reef structures to record sediment changes resulting from the reef materials.
Core samples were not taken around the streetcars or automobile bodies because we soon determined that they were unsuitable materials for long-term artificial habitat. Above the core is a cm rule. Our diving observations, coupled with our sediment analyses, illustrated that marked alterations of the sediment composition and sea floor topography occurred adjacent to the concrete shelters, automobile bodies and the streetcars.
Only negligible differences were detected around the rockpiles. Coarser sediments were uncovered as accelerated currents, produced by openings in the materials, carried away the finer silts and clays.
These depressions re-filled with silt during periods of minimal bottom current, often half covering the concrete shelters [ Figure 14 ]. We suspect that single shelters may eventually "sand-in" completely due to this alternate scouring and filling process. The fish is a sand bass.
Cores taken adjacent to the concrete shelters, in scoured areas, contained coarser fractions than cores taken some distance away. Cores taken adjacent to, and a measured distance from the rock components, did not differ significantly Table 2.
The sediments eventually enclosed half of the inch opening. Turner workers have either used test blocks or made scrapings to collect and describe fouling communities.
In order to obtain some knowledge of attaching organisms during the first year of reef life, we placed several series of test blocks on the various reef materials. By augmenting our general observations in this manner we obtained both quantitative and qualitative measures of the biota.
We assumed that settlement in the first months would be random and indicative of the larvae suspended in the water column, giving a rough indication of larval "preference" for a particular material, while in later months the speciation might be influenced more by the organisms already attached.
Analysis of data obtained from these test series Appendixes 1 and 2 indicated the early settlers caused only minor changes in speciation without appreciable change in the general successional stages encountered. The slight variations noted on the reef materials were likely a function of material texture, and were readily discernible in our general observations. Ideally, our test blocks should have been of the same substances used for reef construction: We used only wooden blocks, however, due to the ease of handling and standardizing their size and shape.
In all, blocks were placed in this manner. Each month one block was removed from each series and placed in a wide-mouth quart jar, underwater. Ebert recording conditions on the reef during the first month when we affixed a test block series to 9 of the 12 reef components.
The various organisms were sorted into phyla and subsequently identified to lower taxons.
Man-Made Reef Ecology
Because of time and personnel limitations we did not identify all the organisms to generic or specific levels. Polychaete worms, for example, were diagnosed only to family, but at this level the habitat of these worms is fairly well established sedentary or errant and their trophic level and entry into the food chain can be postulated. Unfortunately, wood-boring organisms severely infected the test blocks, preventing complete recovery of all the blocks for analysis. The empty burrows of the wood-borers also provided a "preferred" habitat for certain organisms whose numbers might otherwise have been lower.
Wood-boring isopods, Limnoria tripunctata, occurred only at Hermosa Beach, being first recorded in December The shipworm Bankia setacea was established first at Malibu concrete shelter series, November and then at Santa Monica rockpile series, December and finally at Hermosa Beach rockpile series, January Despite the earlier settlement of shipworms at Santa Monica and Malibu, we recovered a full complement of 12 test blocks from the Malibu streetcar and Santa Monica concrete shelter series.
The series at Hermosa Beach lasted only 10 months from the time of placement. Although several months often elapsed between the recovery of a particular block and its examination, a comparison of the species found on the blocks, particularly any first occurrences, corresponded within a few days of the dates when we first observed these animals during our more general surveys.
Thus, it was soon apparent that we were not overlooking any major biotic changes during our more casual observations. Since our data are most complete from the Hermosa Beach reef, a descriptive summary of these blocks, listed by material, is presented below, chronologically for individual blocks. These data are then compared with those from the other reefs.
Hermosa Beach Reef Test blocks were attached to the Hermosa Beach reef on September 6,one series on each of the four materials. At this time, tiny acorn barnacles and sparse hydroid growths first observed September 2,only 18 days after the reef placement were already visible on the reef proper.
This was removed October 6,30 days after placement of the series. Acorn barnacles 73 individuals were evenly spaced on the block surfaces and were the dominant organism.
Most were small, with maximum diameters of 5 mm about 0. This was removed November 7,62 days after placement. Sixty evenly distributed acorn barnacles were noted, with maximum diameters of 1. Few other organisms were present. This was removed December 9,94 days after placement. Shortly before this date, the test series was torn loose by a commercial fishing net snagged on the streetcar. After locating the series several feet away, on the sand, we reaffixed it to the streetcar and removed the third block.
The full effect of this disturbance upon the attached organisms was not assessed. The first borers 4 surface boring gribbles, Limnoria tripunctata were recorded. This was removed January 18,days after placement. Moderate hydroid colonies were evenly distributed on all block surfaces. Eight barnacles, maximum diameters of 1 cm about 0. The wood boring mollusk Xylophaga sp. Numerous other organisms including polychaete worms, kelp scallops Leptopecten latiauratusand gammarid and caprellid amphipods were also recorded.
This was removed February 10,days after placement. Moderate hydroid growth covered all of its surfaces except one end where an encrusting ectoproct had established.
Seven live and two dead barnacles, five small shipworms Bankia setaceapolychaete worms, gammarid amphipods, polyclad flatworms and a half-slipper snail Crepipatella lingulata were also present. This was removed March 7,days after placement. The hydroid growth had decreased slightly from the previous month, and 19 live and 2 dead barnacles were present on the upper surface and sides of the block.
How to tell barnacles, limpets and oysters apart on the Shores of Singapore
The barnacles had presumably succumbed to predation by a polyclad flatworm found inhabiting their empty shells. Woodboring activities were extensive with some burrows exceeding 8 cm slightly over 3 inches in length. This was removed April 5,days after placement. The posterior position of the bar and the deeply forked caudal fin tail distinguish it from sargo. The California record fish weighed 1 lb 15 oz and was taken at Long Beach in Unverified report to Port Wrangell, Alaska.
Pileperch from the Elephant Rock Pier Habitat: Shallow-water, rocky-areas, and around piers and docks, both oceanfront and in bays. All agree they are primarily day feeders seeking out large, hard-shelled invertebrates that they are able to crush with their well developed, fused pharyngeal tooth plates. Since other perch do not share this ability, some scientists feel pile perch should be placed in a separate genus —Danalichthys.
Foods include crabs, brittle stars, sand dollars, barnacles, bean clams, whole mussels, limpets, dove shells, California cones, Norris top shells, and chitons. Pile perch are taken at virtually every pier in California but the largest numbers are taken at Bay Area piers.
A favored species for shore anglers fishing in bays throughout the state. An inshore species sometimes taken by boaters fishing in bays, especially San Francisco Bay. Pileperch from the Goleta Pier Bait and Tackle: Pile perch can be exasperatingly difficult to catch. The large perch will often be seen placidly swimming in clear view around the mussel-covered pilings while refusing to partake of the offerings of the gods up above—anglers whose mojo is evidently on empty.
Perhaps their pea-sized brains are distracted and normal caution takes a back seat to other thoughts? Best bait in southern California seems to be fresh mussels, rock crabs or bloodworms.