Overall Score 82/100

Hannah Nolan

June 4th, 2012

KFE Spring 2012

Overall score 82/100

Title [[3/4 – usually titles aren’t questions and you should probably mention species-habitat associations]]

Are Fish Species Accumulation and Relative Abundance at Hopkins Marine Station a Function of Zone?

Clarity [[12/14 – overall pretty clear writing style, but you need to focus on connecting your sentences so that they build upon one another and relationships between ideas are explicit, not just implied.]]

Introduction [[15/20]]

Habitat complexity lends to greater species abundance and accumulation (Heck, 1977; Tews, 2004; Dean, 1999). Central California reefs are characterized by both complex kelp forest habitat, and less complex sandy habitat .The kelp forest is considered complex because of the presence of canopy-creating algae like Macrocystispyrifera, and bedrock with varying relief. Kelp forest fishes utilize more complex habitat structure because there tends to be more abundance of higher-quality prey (Schmitt, 1985; Ebeling, 1985), andthere is more refuge from predators for both adult and juvenile fish (Holbrook 1986; Carr 1991; Dean 1999). Fish assemblages tend to be greater and more diverse when Macrocystispyrifera (giant-kelp) is present, because of the habitat that it creates as a three-dimensional structure (Bodkin, 1986). [[good use of the literature. Would be better if you got into the broad ecological questions a little more]]

Our study addresses the question of abundance and accumulation as a function of habitat complexity by looking at the different zones (shallow and deep) at Hopkins Marine Station in Pacific Grove, California. Previous studies that we have perreformed at Hopkins reef have shown that there is a greater presence of bedrock, Macrocystispyrifera and Cystoseiraosmundacea in the shallow zone, and that the deep zone is characterized by flat, sandy bottom [[isn’t that a gross oversimplification?]](KFE UPC survey, 2012).

In this study we look at fish species accumulation and abundance as a function of zone at Hopkins Reef. We hypothesize that relative fish species abundance will be greater in the shallow zone (6-8 meters) than in the deep zone (9-10 meters). Previous studies we have preformed at the site have shown that there is more complex habitat structure in the shallow zone (KFE UPC Study, 2012). We also hypothesize that fish species accumulation will be greater in the shallow zone because there is a greater presence of bedrock and Macrocystis.

The kelp forest is an excellent system for examining whether or not fish assemblages are dependent on habitat complexity. Giant kelp is a complex structure with a canopy, a mid-water section, and an understory that is attached to rocky substrate. The different sections of kelp in the water column create different types of habitat that is utilized by kelp forest fishes (Bodkin, 1986; Carr, 1991). The central California kelp forest is characterized by diversity in Sebastes (rockfish), and Embiotocids (surfperches), as well as several species of Hexagrammids (greenlings), and a number of other individual species from different genuses. This is the first time that a UC Santa Cruz kelp forest ecology class has collected data as a group, and the first time that we have collected data in the spring (April-June). To our knowledge, this approach has not yet been done at Hopkins Reef.

Methods [[16/18 – nice job]]

General Approach

In order to identify the substrate type and relief we conducted an observational study by using a uniform point contact (UPC) survey on April 10th, 2012. Uniform point contact is a good way to characterize the bottom of a system. On April 17th, 2012 we preformed an algae swath to count the number of Cystoseiraosmundacea and Macrocystispyrifera individuals in our system. On April 24th, 2012 we conducted another observational study, and did a fish survey of Hopkins reef. Fish surveys help give a snapshot of the relative abundance of species in a system, and the accumulation of fish species. The UPC data gives us a picture of what the bottom of the system looks like in the offshore (deep) and onshore (shallow) parts of the reef. Our fish survey data combined with UPC data allows us to determine whether or not the fish live in more complex habitat. [[good job mentioning all three sources of data and how they contributed to the study]]

Hopkins Reef as a System

The study occurred at Hopkins Marine Station (36°37’13.23”N, 121°54’07.95”W) in Pacific Grove, California. Hopkins reef is a kelp forest growing on a granitic substrate. The reef is unusual because it lacks a Pterygopheracalifornicaunderstory, and instead has an understory of Cystoseiraosmundacea, as well as other brown and red algae species. The canopy is mostlyMacrocystispyrifera, with some reproductiveCystoseiraosmundacea. Hopkins is a no-take marine reserve, which makes it an excellent study site for examining a reef without the presence of fishermen.

Hopkins has a rich diversity of different habitat types. The shallow zone is mostly characterized by bedrock substrate with shallow relief, and the deep zone is characterized by a flat sandy bottom (KFE UPC Survey, 2012). The kelp forest contains lush Macrocystispyrifera and Cystoseiraosmundacea. The wide range of habitat structure, and presence of large algae lends to a great diversity of invertebrate and fish species, which makes it an interesting system for looking at species associations and interactions.

Study Design

Hypothesis One- There is more relative abundance of fish species in the shallow zone because of the more complex habitat structure

Relative species abundance as a function of zone is analyzed using a chi-square analysis. The chi-square analysis is based on the raw number of observed fish. The chi-square analysis tests the independence of the predictor variables. In this case the predictor variables are abundance and zone. In this analysis, the null hypothesis assumes that abundance and zone are independent of one another. If the p-value is not significant, then there is no difference in the relative abundance of fish as a function of zone. If the p-value is significant, then we can assume that the relative abundance of fish species varies by zone.

UPC and swath data maps the percentage of relief type, substrate type, and presence of macro-algae as a function of zone. The swath data shows a stronger presence of Macrocystispyrifera and Cystoseiraosmundaceain the shallow zone, as well as a habitat characterized by bedrock (KFE UPC and Swath survey, 2012). The presence of Cystoseira, Macrocystis, and bedrock creates a more complex habitat structure. Our hypothesis assumes that there will be more fish in the shallow zone because of the more complex habitat structure. If our hypothesis is correct, and relative fish abundance varies by zone, then our graph will show more relative fish abundance in the shallow zone.

Hypothesis Two- There is more accumulation of fish species in the shallow zone because of the more complex habitat structure

A line is plotted on a graph that represents the expected number of species that will be found as a function of the number of segments sampled in each zone. There are a total of 36 segments. Each value is obtained by re-sampling the data. The value represents the best estimate of species per defined number of segments. The asymptote of the line is the maximum number of species we expect to find in the zone. The initial slope represents how common certain fish species are. The greater the initial slope, the more even the species abundance is. Evenness is the distribution of species within a habitat, the more even the fish accumulation, the more likely we will encounter different species of fish on a transect. If the slope of the line for the shallow zone is greater, and the asymptote higher than the deep zone on the graph, then we can assume that fish accumulate more and are more evenly distributed in the shallow zone than in the deep zone. [[good description of how you analyze and interpret your data relative to your hypotheses]]

Data Collection

Uniform Point Contact (UPC) Data was collected by a group of undergraduate students on SCUBA on April 10th, 2012 between 8-11 in the morning. In pairs,we were located at ten points along a permanent transect line in five meter increments between the 90 and 135 meter marks. We swam along a 30-meter tape, placed our finger down every fifty centimeters, and then recorded the substrate, relief, the presence of drift kelp or juvenile laminarias, and the sessile organism. The meter tapes were laid out at 90° offshore, and 270° onshore.

The fish survey was performed on April 24th, 2012. Buddy pairs swam down a 30-meter transect line, with one individual located in the front and the other individual swimming behind. Fish were counted in five meter long segments that were two meters high, and two meters wide. We counted fish commonly seen in central California, including several species of Sebastes, Embiotocids, and Hexagrammids. One transect was laid out 270° onshore, and the other transect was laid out 90° offshore. 36 total segments were calculated in the data. [[what about the sqath survey for macroalgae?]]

Results [[13/16]]

Hypothesis One- there is more relative fish species abundance in the shallow zone

The chi-square value is about 66 and the p-value is <0.000001, therefore we can assume that relative fish abundance is dependent on zone (Fig 1). When the mean number of fish per transects is plotted against species, we see that there is generally a higher mean for most species in the deep zone (Fig 2). The only exceptions are Rhinogobiopsnicholsi (black-eyed goby) and Sebasteschyrsomelas(black and yellow rockfish), which have a higher mean in the shallow zone (Fig 2). The graph represents fish density as a function of zone.

The second graph (Fig 3) plots percentage against the different species counted. Again we see a generally higher percentage of fish species in the deep zone rather than in the shallow zone. The exceptions are again the black-eyed goby and the black and yellow rockfish, with the addition of the painted greenling, kelp greenling, and striped surfperch having a higher percentage of species abundance in the shallow zone (Fig 3).

Hypothesis Two- there is more fish species accumulation in the shallow zone

Accumulated species is plotted against the number of segments to create two asymptotic curves, one curve representing the deep zone and the other curve representing the shallow zone (Fig 4). The line for the shallow zone does not have as steep of an initial slope as the line for the deep zone, and begins to asymptote at around 14. The line for the deep zone has a steeper initial slope and does not asymptote on the graph, indicating that it will asymptote at a larger number of accumulated species.

Discussion [[17/22]]

Hypothesis One- there is more relative fish species abundance in the shallow zone because of the more complex habitat structure

Our study shows that rather than having greater relative fish species abundance in the more complex shallow zone, there is more species abundance in the less complex deep zone. This could be because there could beless disturbance in the deep zone rather than in the shallow zone. According to the Intermediate Disturbance Hypothesis, a lot of disturbance in a system can lead to fewer species because the amount of disturbance limits successional species from taking the place of the earlier settled species (Connell, 1978). However, little to no disturbance in a system prevents competition from taking place, and prevents less competitive species from living in the system (Connell, 1978). The deep zone may be experiencing less disturbance than the shallow zone, but in order to determine if this is the case we would have to experiment further in the different zones.

I have also personally observed more drift algae over the sandy bottom in the deep zone at transects where I have collected data. Lenanton and Caputi hypothesized that drift algae creates a more complex habitat that can be utilized by juvenile fish for shelter and for food, however they also observed that juvenile fish move towards drift algae at night because there is less risk of predation (1988). We have not quantified the amount of drift algae that is in the shallow zone and in the deep zone. In order to determine if there is a greater presence of drift algae in the deep zone we will have to survey the amount of drift in both zones.

Some fish species are found to be in greater percentage in the shallow zone rather than in the deep zone. Rhinogobiopsnicholsii(black-eyed goby) has both a greater mean and greater percentage in the shallow zone. Rhinogobiopsnicholsiiis closely tied with the edges of bedrock on the sandy bottom (Csepp, 1999).The segments we used in our data analyses might have been from some of the areas in the shallow zone where there is more sand than bedrockbecause the data shows a greater abundance of R. nicholsii in the shallow zone. Sebasteschrysomelas also had a greater mean and percentage in the shallow zone rather than in the deep zone. Larson showed that S. chrysomelasoutcompetes S. carnatus(gopher rockfish) for more desirable habitat with more prey, and therefore is found to be at shallower depths in the water column (1980). Our data corresponds with this study because we found more S. chrysomelas in the shallow zone, and more S. carnatus in the deep zone. Since S. chrysomelasoutcompetesS. carnatus for better habitat, we should be able to hypothesize that there will be more fish abundance where S. chrysomelas is found [[why?]].

It should be noted that our study size is very small. Our study occurred on one day out of the year, and only 36 segments were used in the data calculation. On the day that we preformed the study, the water was murky, and the visibility was poor (only about two meters). It was also our first time counting fish, so there might be human error in the data (not spotting fish, incorrect identification). There was a school of pile perch that day that kept getting scared into each of the buddy pairs transects, which accounts for why pile perch (Damalicthysvacca) are 40% of the fish abundance. Error in the data, small sample size, and murky conditions might account for why our data shows greater abundance and accumulation of fish in the deep zone. We need a larger sample size in order to determine whether or not there really is more relative abundance of fish in the deep zone.

Previous studies that have been done on fish abundance in complex habitat have shown that kelp forest fish are more abundant when kelp is present (Bodkin, 1986). Our study should have shown a greater abundance of fish in the shallow zone where there is more kelp and complex structures. Stephens has suggested that the presence of kelp is not necessarily what leads to the abundance of fish, but rather the presence of high relief structures (1984). High relief only characterizes about 5% of the bottom of Hopkins, and most of it is found in the shallow zone (KFE UPC Survey, 2012). In order to determine whether or not there truly is a greater relative abundance of fish species in the deep zone we will have to conduct more fish surveys at Hopkins reef. Mechanisms for why there is greater relative abundance of species in the deep zone remain unclear, but could possibly be attributed to less disturbance and more drift algae. In order to determine whether or not these are the case we need to conduct studies on whether or not there is more drift algae in the deep zone than in the shallow, and test to see if the deep zone is not as disturbed.

Hypothesis Two- There is more fish species accumulation in the shallow zone because of the more complex habitat structure.

Our graph shows that there is a steeper initial slope for the deep zone than for the shallow zone, which indicates that species are more common in the deep zone than in the shallow zone (Fig 4). The line for the shallow zone asymptotes at about 14, whereas the line for the deep zone has not yet reached its asymptote (Fig 4). This implies that we should find more species in the deep zone than in the shallow zone, and that species accumulation is more even in the deep zone than in the shallow. Evenness means that we are more likely to find different species across all transects rather than one species more than the others.

Why there is greater accumulation of species in the deep zone than in the shallow zone is perplexing. Less disturbance might be an explanation, but further studies would have to be preformed in order to determine whether or not disturbance is the cause. Like fish abundance, we would expect to see a greater accumulation of species in the shallow zone where there is more complex habitat structure, and a greater presence of canopy building kelps like Macrocystispyrifera and Cystoseiraosmundacea(Bodkin, 1986; Ebeling, 1988; Carr, 1991; Dean, 2000). It should be noted that the deep zone at Hopkins does not lack kelp, but that there is less of it (KFE Swath Data, 2012). In order to determine whether or not there really is more accumulation of species in the deep zone than in the shallow zone we need to conduct more fish surveys and gather more data.